Pressor Dose Research Articles

Pathophysiologic Vasodilation in Cardiogenic Shock and Its Impact on Mortality.

Cardiogenic shock (CS) mortality remains near 40%. In addition to inadequate cardiac output, patients with severe CS may exhibit vasodilation. We aimed to examine the prevalence and consequences of vasodilation in CS. We analyzed all patients hospitalized at a CS referral center who were diagnosed with CS stages B to E and did not have concurrent sepsis or recent cardiac surgery. Vasodilation was defined by lower systemic vascular resistance (SVR), higher norepinephrine equivalent dose, or a blunted SVR response to pressors. Threshold SVR values were determined by their relation to 14-day mortality in spline models. The primary outcome was death within 14 days of CS onset in multivariable-adjusted Cox models. This study included 713 patients with a mean age of 60 years and 27% females; 14-day mortality was 28%, and 38% were vasodilated. The median SVR was 1308 dynes•s•cm-5 (interquartile range, 870-1652), median norepinephrine equivalent was 0.11 µg/kg per minute (interquartile range, 0-0.2), and 28% had a blunted pressor response. Each 100-dynes•s•cm-5 decrease in SVR below 800 was associated with 20% higher mortality (adjusted hazard ratio, 1.23; P=0.004). Each 0.1-µg/kg per minute increase in norepinephrine equivalent dose was associated with 15% higher mortality (adjusted hazard ratio, 1.12; P<0.001). A blunted pressor response was associated with a nearly 2-fold mortality increase (adjusted hazard ratio, 1.74; P=0.003). Pathophysiologic vasodilation is prevalent in CS and independently associated with an increased risk of death. CS vasodilation can be identified by SVR <800 dynes•s•cm-5, high doses of pressors, or a blunted SVR response to pressors. Additional studies exploring mechanisms and treatments for CS vasodilation are needed.

The Role of Interleukin-6 in Regulating Glomerular Filtration Rate during Angiotensin II and High Salt Conditions

Previous results demonstrate that interleukin-6 (IL-6) increases mean arterial pressure (MAP) during Angiotensin II (Ang II)-salt hypertension. In addition, albumin excretion was lower in IL-6 knockout mice (KO) when compared to wild-type (WT). This study investigated the role of IL-6 on regulating glomerular filtration rate (GFR), renal plasma flow (RPF) and MAP in WT and IL-6 KO mice treated with a slow pressor dose of Ang II (200 ng/kg/min) +/- 6% high-salt (HS) diet. Male C57BL6 and IL-6 KO mice (12 weeks old) were treated with Ang II +/- 6% HS diet for 12 – 14 days. Mean arterial pressure, RPF and GFR were measured in anesthetized mice. MAP was 130 ± 7 mmHg and 91 ± 4 mmHg in control WT and IL-6 KO mice, respectively. Ang II treatment increased MAP in WT (153 ± 5 mmHg) and no change in IL-6 KO (83 ± 4 mmHg) mice. Ang II + 6% HS increased MAP to 150 ± 11 mmHg in WT and 93 ± 4 mmHg in IL-6 KO mice. Baseline RPF was 1822 ± 229 and 1912 ± 402 ml/min/g in control WT and IL-6 KO mice, respectively. Ang II treatment increased RPF in WT (3156 ± 753 ml/min/g), while lowering RPF in IL-6 KO (1648 ± 422 ml/min/g) mice. RPF during Ang II + 6% HS treatment was decreased in WT (1095 ± 305 ml/min/g) and IL-6 KO (1133 ml/min/g) mice. GFR was 756 ± ml/min/g and 788 ± ml/min/g in control WT and IL-6 KO mice, respectively. Ang II increased GFR in WT (1009 ± 63 ml/min/g) and no change in IL-6 KO (756 ± 23 ml/min/g). Ang II + 6% HS increased GFR in WT (1095 ± 146 ml/min/g) and no change in GFR of IL-6 KO (540 ± 207 ml/min/g) mice. Our results suggest that IL-6 reduces MAP during baseline, Ang II, and Ang II + 6% HS. The absence of IL-6 prevented increases in MAP, RPF and GFR during Ang II treatment. Our data also suggest that IL-6 contributes to increased MAP and GFR during Ang II + 6% HS treatment. K01HL092593-05. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Deletion of dipeptidyl peptidase 4 attenuates angiotensin II-induced blood pressure rise and enhances NHE3 phosphorylation at serine 552 in the kidneys of male and female mice

Dipeptidyl peptidase 4 (DPP4) physically associates with the Na+/H+ exchanger isoform3 (NHE3), and DPP4 inhibitors reduce NHE3-dependent sodium reabsorption in the renal proximal tubule. Angiotensin II (Ang II) is a key mediator of sodium and water retention by the kidneys, partly through the activation of proximal tubule NHE3. Recent studies from our group reveled that Ang II activates DPP4 by, both in vivo and in vitro, and that inhibition of several canonical and non-canonical pathways can suppress this activation. However, the impact of this interaction on renal sodium handling and blood pressure remains unclear. This study aimed to test the hypothesis that DPP4 deletion mitigates the blood pressure elevation induced by Ang II in male and female mice, at least partly due to the downregulation of NHE3 in the renal proximal tubule. Male and female mice with global DPP4 deletion or wild-type controls were acutely administered either a pressor dose of Ang II (1000 ng/kg/minute) or saline. Blood pressure was measured before and one hour after the administration of Ang II or saline by tail-cuff plethysmography. Kidneys were subsequently collected for protein homogenate preparation. Increased DPP4 activity was observed in response to acute Ang II stimulation in both male and female wild-type mice, with female mice exhibiting higher basal DPP4 activity. As expected, DPP4 knockout mice exhibited minimal DPP4 activity. Baseline blood pressure did not differ significantly between male wild-type and DPP4 knockout mice or between females. In line with our hypothesis, both male and female DPP4 knockout mice displayed a reduced increase in blood pressure in response to acute Ang II administration compared to their wild-type counterparts. Furthermore, the phosphorylation of NHE3 at serine 552 (pS552-NHE3), a surrogate marker of NHE3 inhibition, was higher in wild-type females than males. Interestingly, pS552-NHE3 was fivefold higher in male DPP4 knockout mice and threefold higher in female DPP4 knockout mice compared to their wild-type counterparts. Additionally, the increase in pS552-NHE3 one hour after Ang II administration was higher in males (1208 ± 119 vs. 544 ± 54 %, P &lt; 0.01) and females (385 ± 18 vs. 271 ± 27%, P &lt; 0.01) DPP4 knockout mice compared to wild-type animals. Moreover, ERK, a well-known effector of the AT1R signaling cascade, was phosphorylated in a similar manner as NHE3 in response to Ang II in males but not in females. In conclusion, our data demonstrate that the absence of DPP4 reduces the rise in blood pressure induced by acute Ang II stimulation, possibly through Ang II/AT1R signaling pathways influencing phosphorylation of downstream effectors such as NHE3. Furthermore, we observe significant sex differences in Ang II effects on DPP4 activity, and AT1R signaling cascades. FAPESP 2021/14524-3 NIDDKD - K08DK115886. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pressor Dose Vasopressin-Induced Acute Hyponatremia

Pressor Dose Vasopressin-Induced Acute Hyponatremia

Angiotensin II-Induced Memory γδ T Cells Sensitize Mice to a Mild Hypertensive Stimulus.

Memory T cells develop during an initial hypertensive episode, sensitizing mice to develop hypertension from further mild hypertensive challenges. We hypothesized that memory γδ T cells develop after a hypertensive challenge and sensitize mice to develop hypertension in response to a subsequent mild hypertensive challenge. The first aim was to profile memory γδ T cells after a 14-day pressor dose angiotensin II (AngII) infusion (490 ng/kg/min, subcutaneously) in male mice. The second aim was to deplete γδ T cells during a second 14-day subpressor dose AngII challenge (140 ng/kg/min, subcutaneously) in mice pre-exposed to an initial pressor dose AngII challenge. The third aim was to transfer 2.5 × 105 live pre-activated or not γδ T cells from mice that had received a 14-day pressor dose AngII infusion or sham treatment, to naive recipient mice stimulated with a subpressor dose AngII infusion. Effector memory γδ T cells increased 5.2-fold in mesenteric vessels and perivascular adipose tissue, and 1.8-fold in mesenteric lymph nodes in pressor dose AngII-infused mice compared with sham-treated mice. Mice depleted of γδ T cells had 14 mm Hg lower systolic blood pressure (SBP) elevation than control mice from day 7 to 14 of subpressor dose AngII infusion. Adoptive transfer of γδ T cells from hypertensive mice induced an 18 mm Hg higher SBP elevation compared with a subpressor dose AngII infusion vs. γδ T cells transferred from sham-treated mice. Memory γδ T cells develop in response to hypertensive stimuli, and contribute to the pathogenesis of hypertension.

Abstract P3124: Chronic Infusion Of Angiotensin II Promotes Ventricular Fibrosis And Diastolic Dysfunction In Aging Male But Not Female Mouse Hearts

Heart failure prevalence increases with age and affects men and women differently. Chronic activation of the renin-angiotensin system (RAS) in heart failure increases circulating angiotensin II (AII) levels, which elevates blood pressure (BP), promotes fibrosis and leads to adverse remodelling of the heart. Whether maladaptive responses to AII differ between the sexes at older ages is unclear, as most studies use young male animal models. We investigated whether adverse cardiac remodeling induced by chronic exposure to AII differed between the sexes in older C57BL/6 mice. Osmotic minipumps with pressor doses of AII (3 mg/kg/day) or saline were implanted into older mice (≈16 mos) of both sexes for 6 weeks. BP (tail cuff) and ventricular structure/function (echocardiography) were measured at baseline, midpoint, and endpoint. Ventricular fibrosis markers (transforming growth factor-ß (TGF-ß), fibronectin collagen I, collagen III) were quantified with qPCR. Mean arterial pressure increased similarly in both sexes (76.3±4.2 vs. 136.1±4.6 mmHg in males and 73.9±2.9 vs. 116.1±8.7 mmHg in females; p&lt;0.05; n=6-8/group). AII infusion also increased LV mass and reduced ejection fraction in males and females. By contrast, AII increased signs of diastolic dysfunction in males but had little impact on diastolic function in females. For example, isovolumic relaxation time increased over 6 weeks of AII infusion in males (11.7±1.0 vs. 19.0±1.4 ms; p&lt;0.05) but not in females (14.6±0.9 vs. 16.4±1.2 ms). Similar results were seen for E/A ratios. Molecular studies showed a marked increase in mRNA abundance for TGF-ß in male ventricles (1.02±0.13 vs. 1.50±0.16; p&lt;0.05) but not in females (1.01±0.08 vs. 1.25±0.10). Similar male-female differences were seen for collagens I and III (fibronectin was similar in both sexes, and not affected by AII). As TGF-ß signalling increases the production of profibrotic mediators like collagens I and III, these findings suggest that chronic RAS activation increases fibrosis and disrupts diastolic function in aging male hearts. By contrast, older female hearts are resistant to these deleterious effects of RAS activation. These sex-specific differences may modify heart failure expression and responses to treatment in older men and women.

Regulation of renal function by the peroxisome proliferator-activated receptor-alpha: A novel target for treating hypertension

Approximately 37 million people in the U.S. have chronic kidney disease, which is a major risk factor for cardiovascular and end stage renal diseases. We have identified a nuclear receptor, peroxisome proliferator-activated receptor – alpha (PPAR-α), that plays a major role in regulating renal glomerular filtration rate in an experimental model of hypertension. Targeting PPAR-α signaling provides novel therapeutic strategies for reducing hypertension associated chronic kidney disease. PPAR-α knockout (KO) mice exhibit increased renal inflammation and blood pressure response to Angiotensin II (Ang II). In this study, we investigated the role of PPAR-α in renal function in a mouse model of hypertension. Male 4-month-old wild type (WT) and PPAR-α KO mice were instrumented with radio transmitters by artery canulation (Data Science International). This method minimizes stress and artifacts by avoiding the use of tethering, restraining, or anesthetizing the mice during data sampling. After recovery from surgery, we continuously measured mean arterial pressure (MAP) via radio telemetry in conscious ambulatory mice. After baseline MAP was established, vehicle (Veh; saline) or Ang II were infused using an osmotic minipump at a slow pressor dose (400 ng/kg/min) for 12 days. On day 12, we injected an intravenous bolus of fluorescin-sinistrin (3.74 ml/g body weight) and collected 8 blood samples (20 μl/sample) during a 75-minute period to enable calculation of the glomerular filtration rate (GFR) using [GFR = I/(A/a + B/b]. Similar to our prior observations, no significant (ns) differences in baseline MAP were observed between WT and PPAR-α KO mice [(mmHg): WT (n=6), 111±20 vs. PPAR-α KO (n=6), 113 ± 10; ns] whereas after 12 days of the slow pressor effect of Ang II, MAP was increased in both strains [(mmHg): WT (n=8), 138 ± 11# vs. PPAR-α KO (n=8), 156 ± 16#; #p&lt;0.05 vs. basal, same strain]; however, the increase in MAP was greater in the PPAR-α KO (43 mmHg) compared to WT (27 mmHg) mice. The absence of PPAR-α reduced GFR by 24% under basal conditions [(μl/min): WT (n=3), 346 ± 20 vs. PPAR-α KO (n=3), 275 ± 27*, *p&lt;0.05 vs WT]. After 12 days of Ang II infusion, GFR was reduced in WT mice by 27% and did not further reduce GFR in PPAR-α KO mice [(μl/min): WT (n=6), 251 ± 11# vs. PPAR-α KO (n=6), 277 ± 61; #p&lt;0.05 vs. basal, same strain]. PPAR-α protects mice from worsening hypertension and is critical to preserving GFR during normotensive conditions. Ongoing studies are further investigating how PPAR-α regulates renal function. These finding suggest therapeutics designed to increase PPAR-α activity could have clinical benefit in chronic kidney disease. Howard University Research Centers at Minority Institutions, Georgetown-Howard Universities Center for Clinical and Translational Science, Howard University Aging Grant, K01HL092593 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

378 Regulation of renal function by the peroxisome proliferator-activated receptor-alpha: A novel target for treating hypertension

OBJECTIVES/GOALS: Approximately 37 million people in the U.S. have chronic kidney disease, which is a major risk factor for cardiovascular and end stage renal diseases. PPAR-αknockout (KO) mice exhibit increased renal inflammation and blood pressure. In this study, we investigated the role of PPAR-αin renal function in a mouse model of hypertension. METHODS/STUDY POPULATION: Male 4-month-old wild type (WT) and PPAR-αKO mice were instrumented with radio transmitters by artery canulation (Data Science Intl). This method minimizes stress and artifacts by avoiding the use of tethering, restraining, or anesthetizing the mice during data sampling. After recovery from surgery, we continuously measured mean arterial pressure (MAP) via radio telemetry in conscious ambulatory mice. After baseline MAP was established, vehicle (Veh; saline) or angiotensin II (Ang II) were infused using an osmotic minipump at a slow pressor dose (400 ng/kg/min) for 12 days. On day 12, we injected an intravenous bolus of fluorescin-sinistrin (3.74µl/g body weight) and collected 8 blood samples (20µl/sample) over 75 minutes to enable calculation of the glomerular filtration rate (GFR) using [GFR = I/(A/α+ B/ß)]. RESULTS/ANTICIPATED RESULTS: Similar to our prior observations, no significant (ns) differences in baseline MAP were observed between WT and PPAR-αKO mice [(mmHg): WT (n=6), 111 ± 20 vs. PPAR-αKO (n=6), 113 ± 10; ns] whereas after 12 days of the slow pressor effect of Ang II, MAP was increased in both strains [(mmHg): WT (n=8), 138 ± 11# vs. PPAR-αKO (n=8) , 156 ± 16#; #p DISCUSSION/SIGNIFICANCE: PPAR-αprotects mice from worsening hypertension and is critical to preserving GFR during normotensive conditions. Ongoing studies are further investigating how PPAR-αregulates renal function. These finding suggest therapeutics designed to increase PPAR-αactivity could have clinical benefit in chronic kidney disease.

S-40-3: MEMORY GAMMA DELTA T CELLS PLAY A ROLE IN HYPERTENSION

Objectives: A subset of T cells, γδ T cells, participate in the pathogenesis of hypertension. It has been shown that memory T cells develop after a hypertensive insult and sensitize mice to develop hypertension to subsequent mild hypertensive stimuli. However, whether memory γδ T cells develop and play a role in hypertension is unknown. We hypothesize that memory γδ T cells form after a hypertensive challenge, and that they sensitize mice to develop hypertension to mild hypertensive stimuli. Methods: Ten-12-week-old C57BL/6J mice were exposed or not to a pressor dose of angiotensin II (490 ng/kg/min, SC) for two weeks, followed by a two-week washout period, and then infused with a subpressor dose of angiotensin II (140 ng/kg/min, SC) for two weeks. Blood pressure (BP) was measured by telemetry and memory γδ T cells profiled by flow cytometry. A subset of mice was injected IP with 400 μg of anti-T cell receptor γδ-depleting or isotype control antibodies 1 day before and 6 days after the initiation of second hypertensive challenge. A final subset was injected IV with 2.5x105 γδ T cells isolated from hypertensive or normotensive mice, and then exposed to a subpressor dose of angiotensin II as above. Results: Repeated hypertensive challenges yielded a higher systolic BP than one mild hypertensive stimulus (154 ± 4 vs 120 ± 3 mm Hg, P &lt; 0.01). Two-week pressor dose angiotensin II increased effector memory γδ T cells in mesenteric artery perivascular adipose tissue (1.25 ± 0.37% vs. 0.24 ± 0.12%, P &lt; 0.05) and mesenteric lymph nodes (1.49 ± 0.03% vs 0.82 ± 0.15%, P &lt; 0.05). γδ T cell depletion reduced systolic BP elevation from day 8 (135 ± 5 vs 150 ± 5 mm Hg, P &lt; 0.05) to day 13 of the second hypertensive challenge (150 ± 5 vs 163 ± 2 mm Hg, P &lt; 0.05). Adoptive transfer of γδ T cells isolated from hypertensive compared to normotensive mice caused a greater systolic BP elevation in response to a subpressor dose of angiotensin II (159 ± 3 vs 142 ± 6 mm Hg, P &lt; 0.01). Conclusion: Memory γδ T cells develop after a hypertensive challenge and sensitize mice to mild hypertensive stimuli. Memory γδ T cells may represent a novel therapeutic target to treat hypertensive humans.

Abstract P239: Angiotensin II-Induced Memory Gamma Delta T Cells Sensitize Mice To A Mild Hypertensive Stimulus

Hypothesis: We hypothesize that memory γδ T cells form after a hypertensive challenge, and that they sensitize mice to develop hypertension to mild hypertensive stimuli. Methods: Ten-12-week-old C57BL/6J mice were exposed or not to a pressor dose of angiotensin II (490 ng/kg/min, SC) for two weeks, followed by a two-week washout period, and then infused with a subpressor dose of angiotensin II (140 ng/kg/min, SC) for two weeks. Blood pressure (BP) was measured by telemetry and memory γδ T cells profiled by flow cytometry. A subset of mice was injected IP with 400 μg of anti-T cell receptor γδ-depleting or isotype control antibodies 1 day before and 6 days after the initiation of second hypertensive challenge. A final subset was injected IV with 2.5x10 5 γδ T cells isolated from hypertensive or normotensive mice, and then exposed to a subpressor dose of angiotensin II as above. Results: Repeated hypertensive challenges yielded a higher systolic BP than one mild hypertensive stimulus (154±4 vs 120±3 mm Hg, P &lt;0.01). Two-week pressor dose angiotensin II increased effector memory γδ T cells in mesenteric artery perivascular adipose tissue (1.25±0.37% vs. 0.24±0.12%, P&lt;0.05) and mesenteric lymph nodes (1.49±0.03% vs 0.82±0.15%, P&lt;0.05). γδ T cell depletion reduced systolic BP elevation from day 8 (135±5 vs 150±5 mm Hg, P &lt;0.05) to day 13 of the second hypertensive challenge (150±5 vs 163±2 mm Hg, P &lt;0.05). Adoptive transfer of γδ T cells isolated from hypertensive compared to normotensive mice caused a greater systolic BP elevation in response to a subpressor dose of angiotensin II (159±3 vs 142±6 mm Hg, P &lt;0.01). Conclusion: Memory γδ T cells develop after a hypertensive challenge and sensitize mice to mild hypertensive stimuli. Memory γδ T cells may represent a novel therapeutic target to treat hypertensive humans.

Abstract 098: Double Deletion Of At 1a Receptors And Na + /h + Exchanger 3 In The Proximal Tubules Attenuates Angiotensin Ii-induced And 2k1c Goldblatt Hypertension In Proximal Tubule-specific Pt- Agtr1a -/- / Nhe3 -/- Mice

We have previously shown that genetic deletion of AT 1 (AT 1a ) receptors or Na + /H + exchanger 3 (NHE3) selectively in the proximal tubules attenuated the development of angiotensin II (Ang II)-induced hypertension in mice. The present study determined whether double deletion of AT 1a receptors and NHE3 selectively in the proximal tubules further attenuates the development of Ang II-induced or 2-kidney, 1-clip (2K1C) Goldblatt Hypertension. Proximal tubule-specific AT 1a receptor and NHE3 double knockout mice, PT- Agtr1a -/- / Nhe3 -/- , were generated using the iL- Sglt2-Cre / LoxP approach. Adult male wild-type (WT), PT- Agtr1a -/- , PT- Nhe3 -/- , and PT- Agtr1a -/- / Nhe3 -/- double knockout mice were treated with vehicle (or sham as time-controls), a slow pressor dose of Ang II infusion for 2 weeks (500 μg/kg body wt./day, i.p.), or induction of 2K1C Goldblatt hypertension by placing a silver clip (0.12 mm) on the left renal artery for 4 weeks, respectively. In WT mice, control systolic blood pressure was 118 ± 3 mmHg (n=9), which increased to ~143 ± 5 mmHg in response to Ang II infusion ( P &lt;0.01, n=10) or to induction of 2K1C Goldblatt hypertension (n=12, P &lt;0.01). By comparison, control systolic blood pressure was 15 ± 2 mmHg lower in age-matched PT- Agtr1a -/- mice ( P &lt;0.01), or 13 ± 3 mmHg lower in PT- Nhe3 -/- mice than WT mice ( P &lt;0.01). Double deletion of AT 1a receptors and NHE3 selectively in the proximal tubules further but only moderately decreased basal blood pressure to 98 ± 2 mmHg in PT- Agtr1a -/- / Nhe3 -/- double knockout mice ( P &lt;0.05, n=10). In response to Ang II infusion, systolic blood pressure increased only to ~126 ± 3 mmHg in PT- Agtr1a -/- or PT- Nhe3 -/- mice ( P &lt;0.01). Interestingly, 2K1C Goldblatt hypertension was markedly attenuated in PT- Agtr1a -/- (108 ± 3 mmHg, P &lt;0.01, n=10), PT- Nhe3 -/- (110 ± 2 mmHg, P &lt;0.01, n=10), or PT- Agtr1a -/- / Nhe3 -/- double knockout mice (103 ± 2 mmHg, P &lt;0.01, n=8), respectively. Taken together, these data strongly support the hypothesis that the intratubular Ang II/AT 1a receptor/NHE3 signaling plays a key role in maintaining basal blood pressure homeostasis and the full development of Ang II-induced or 2K1C Goldblatt hypertension.

Abstract 110: Cullin3 Deficiency In T Lymphocytes Causes A Lean Phenotype With Increased Carbohydrate Catabolism But Promotes Hypertension And Renal Inflammation

Low body mass is associated with increased risk of death and stroke, but the mechanism is unclear. Cullin3 (Cul3) ubiquitin ligase regulates T lymphocyte polarization, insulin signaling, and blood pressure (BP) and may provide a mechanistic link for the cardiometabolic phenotypes. Deletion of Cul3 in T cells ( Cul3 fl/fl x CD4-Cre , termed CD4-Cul3 -/- ) resulted in 17% lower body weight (BW: CD4-Cul3 -/- vs CD4-Cul3 +/+ littermates, 23.9 ± 0.9 vs 28.7 ± 0.7 g, 12-16 wks old, n = 6, 12, p&lt;0.01) and blunted growth curve (ΔBW over 7 wks: 3.2 ± 0.9 vs 5.0 ± 0.6 g) in male mice. No difference in BW or growth curve was observed in females. Nuclear magnetic resonance analysis found decreased fat mass (6.4 ± 0.4 vs 9.2 ± 0.8 g, n = 10, 13, p &lt; 0.01) in male null mice with no change in lean mass or fluid content. This was confirmed by post-mortem quantitation of inguinal fat and interscapular brown adipose tissue. There was no difference in postprandial blood glucose, but the male null mice exhibited lower area under curve (AUC mg/dL x hr, 543 ± 104 vs 765 ± 40, p &lt; 0.05) in glucose tolerance test (2 g/kg, 5 hr fasting) and developed hypoglycemia and seizure during fasting insulin tolerance test (0.5 U/kg). CD4-Cul3 -/- mice had elevated respiratory exchange ratio (ratio between CO 2 produced by the body and O 2 consumed) (0.83 ± 0.01 vs 0.78 ± 0.01, n= 4, p &lt; 0.05), suggesting a larger reliance on carbohydrates rather than lipids as fuel. Baseline BP was comparable in null and control mice. In response to chronic pressor dose of angiotensin (Ang) II (490 ng/kg/min, s.c. 14 days), CD4-Cul3 -/- mice displayed exaggerated hypertension (systolic BP in mmHg: 164 ± 8.4 vs 150.3 ± 4.9; ΔSBP: 35.3 ± 7.5 vs 15.8 ± 5.3, p &lt; 0.05). Mean and diastolic BP were also greater in the null mice, but there was no difference in heart rate or activity. Ang II-infused CD4-Cul3 -/- mice showed a trend towards increased renal CD3 + T cells and significantly increased CD4 + T helper cells (p &lt; 0.05). Thus, T cell Cul3 deficiency caused a lean phenotype characterized by decreased adiposity, increased carbohydrate catabolism, and augmented Ang II-induced hypertension and renal inflammation. The CD4-Cul3 -/- mice may be a useful model to study the association between low body mass and increased cardiovascular risk in humans.

Vitamin D supplementation at different doses affects the vagal component of the baroreceptor reflex and the Bezold-Jarisch reflex in eutrophic rats.

Vitamin D has been used to prevent several diseases. The 1,25 (OH) 2D3, the active form of vitamin D (VitD), participates in calcium metabolism, and has direct action in various tissues as those of the cardiovascular system binding to the VitD receptor. We investigated whether the supplementation with different doses of VitD affect or not the resting mean arterial pressure (MAP) and heart rate (HR), heart rate variability (HRV), baroreceptor and Bezold-Jarisch reflexes in eutrophic rats. Adult male Wistar rats were randomly assigned in 4 groups (Control, VitD 15, 250, and 3,750 IU/day, n = 6/group). After 3 days of supplementation, MAP and HR recordings were performed in freely moving rats. Baseline (resting) MAP, HR, and HRV showed no difference in Control and VitD groups. Nevertheless, the index of the baroreceptor reflex showed that the bradycardic component of the baroreflex evoked by a pressor dose of phenylephrine (3 μg/kg of b.w.) in bolus injection had a significant increase in rats supplemented with VitD 15 IU/day for 3 days compared to Control animals. No difference was observed in the index of the baroreflex evaluated with phenylephrine in rats treated with VitD 250 and 3,750 IU/day for 3 days in comparison to the Control group. The index of the baroreceptor reflex evaluated with an intravenous bolus injection of a depressor dose of sodium nitroprusside (30 μg/kg of b.w.) showed that the tachycardic component of the baroreflex is not different comparing all groups supplemented with VitD and Control animals. Rats supplemented with VitD 15 IU/day presented exaggerated bradycardic responses to the intravenous injection of phenylbiguanide (PBG, 5 μg/kg of b.w.) compared to Control animals, despite the similar hypotension in both groups. Higher doses of supplementation of VitD (250 and 3,750 IU/day for 3 days) abolished the hypotension and bradycardia induced by PBG. The findings suggest that the supplementation with different doses of VitD (15, 250, and 3,750 IU/day) for 3 days did not affect the resting arterial pressure, heart rate and autonomic modulation on the heart in rats. Despite that, the supplementation with a low dose of VitD (15 IU/day for 3 days) improved the sensitivity of the bradycardic component of the baroreflex, whereas higher doses of supplementation with VitD (250 and 3,750 IU/day for 3 days) were unable to cause such effect. In addition, the Bezold-Jarisch reflex responses can be affected regardless the dose of VitD (15, 250 or 3,750 IU/day) supplementation for 3 days in rats.

Angiotensin Ii‐induced Hypertension and Glomerular and Tubulointerstitial Injury in Mutant Mice With Kidney Proximal Tubule‐selective Deletion of Mitochondrial Nad+‐dependent Deacetylase Sirtuin 3: Focus on Sex Differences

Sirtuin 3 (SIRT3) is a major mitochondrial NAD‐dependent Deacetylase closely involved in energy production, cell metabolism, oxidative stress responses, and mitochondrial homeostasis during hypertension and kidney diseases. However, it remains unknown whether deletion of SIRT3 in the proximal tubules alters the hypertensive and kidney glomerular and tubulointerstitial fibrotic responses to angiotensin II (Ang II) in sex‐dependent manners. In the present study, adult male and female wild‐type (WT) and mutant mice with proximal tubule‐specific deletion of SIRT3, PT‐Sirt3‐/‐, were infused without (time controls) or with a slow pressor dose of Ang II via an osmotic minipump (0.5 mg/kg/day, i.p.), supplemented with a 2% NaCI diet or losartan, 20 mg/kg/day, for 2 weeks. Systolic (SBP), diastolic (DBP), and mean arterial blood (MAP) pressure were determined using the tail‐cuff method, whereas 24 hr. urinary sodium and potassium excretion were determined using a metabolic cage. Serum and urine creatinine were measured using colorimetric assays, whereas glomerular and tubulointerstitial injury was evaluated by Masson’s Trichrome staining. Basal SBP, DBP, and MAP were significantly lower in PT‐Sirt3‐/‐ mice than WT (WT‐SBP: 112 ± 2 vs. PT‐Sirt3‐/‐‐SBP: 93 ± 2 mmHg, P&lt;0,01). The magnitude of Ang II‐induced hypertension was similar between WT and PT‐Sirt3‐/‐ mice with or without losartan treatment. After the establishment of hypertension, both WT and PT‐Sirt3‐/‐ animals significantly increased urine creatinine levels in both males and females (P&lt;0.05). However, male PT‐Sirt3‐/‐ mice had higher urine creatinine excretion than male WT (WT‐Ang II: 734 ± 59 vs PT‐Sirt3‐/‐‐Ang II: 1155 ± 92, µg/mL, P&lt;0.05), but this sex difference was absent in female WT and PT‐Sirt3‐/‐ mice. In general, females had a lower urinary creatinine excretion (UCr) than males. Losartan treatment decreased urinary creatinine excretion in all groups (P&lt;0.05). Similar responses were observed with plasma creatinine levels (SCr), which were higher in PT‐Sirt3‐/‐mice than in WT mice (P&lt;0.05), but without significant sex differences in response to Ang II infusion or losartan treatment. Losartan significantly increased 24 hr urinary potassium and chloride excretion in Ang II‐infused male and female PT‐Sirt3‐/‐ mice (P&lt;0.01). Finally, Ang II‐infused PT‐Sirt3‐/‐ mice showed significant glomerular and renal cortical tubulointerstitial fibrotic responses, compared with WT (P&lt;0.05), without sex differences. Interestingly, losartan treatment did not show decreased fibrotic responses, instead, showed a tendency to higher collagen deposition than in hypertensive PT‐Sirt3‐/‐ mice. In summary and conclusion, male and female PT‐Sirt3‐/‐ mice have lower basal blood pressure, and Ang II‐induced hypertension and renal fibrotic responses are similar in male and female PT‐Sirt3‐/‐ mice without significant sex differences. Our results suggest that AT1a receptors and SIRT3 play important roles in basal blood pressure homeostasis and Ang II‐induced hypertension and glomerular and tubulointerstitial injury in both male and female mice.

Voluntary Exercise Prevents Hypertensive Response Sensitization Induced by Angiotensin II.

Exercise training has profound effects on the renin-angiotensin system, inflammatory cytokines and oxidative stress, all of which affect autonomic nervous system activity and regulate blood pressure (BP) in both physiological and pathophysiological states. Using the Induction-Delay-Expression paradigm, our previous studies demonstrated that various challenges (stressors) during Induction resulted in hypertensive response sensitization (HTRS) during Expression. The present study tested whether voluntary exercise would protect against subpressor angiotensin (ANG) II-induced HTRS in rats. Adult male rats were given access to either “blocked” (sedentary rats) or functional running (exercise rats) wheels for 12 weeks, and the Induction-Delay-Expression paradigm was applied for the rats during the last 4 weeks. A subpressor dose of ANG II given during Induction produced an enhanced hypertensive response to a pressor dose of ANG II given during Expression in sedentary rats in comparison to sedentary animals that received saline (vehicle control) during Induction. Voluntary exercise did not attenuate the pressor dose of ANG II-induced hypertension but prevented the expression of HTRS seen in sedentary animals. Moreover, voluntary exercise reduced body weight gain and feed efficiency, abolished the augmented BP reduction after ganglionic blockade, reversed the increased mRNA expression of pro-hypertensive components, and upregulated mRNA expression of antihypertensive components in the lamina terminalis and hypothalamic paraventricular nucleus, two key brain nuclei involved in the control of sympathetic activity and BP regulation. These results indicate that exercise training plays a beneficial role in preventing HTRS and that this is associated with shifting the balance of the brain prohypertensive and antihypertensive pathways in favor of attenuated central activity driving sympathetic outflow and reduced BP.

Abstract P254: Sex Differences In Angiotensin Ii-induced Hypertension In Mice With Proximal Tubule-specific Deletion Of Mitochondrial Protein Sirtuin 3 In The Kidney

The development of Angiotensin II (Ang II)-induced hypertension is associated with mitochondrial dysfunction and kidney injury. Sirtuin 3 (SIRT3), a key mitochondrial protein, plays an important role in maintaining mitochondrial homeostasis. However, it remains unknown whether deletion of SIRT3 in the proximal tubules will alter the pressor and renal responses to Ang II in sex-different manners. In the present study, adult male, and female wild-type (WT) and mutant mice with proximal tubule-specific knockout of SIRT3, PT- Sirt3 -/- , were infused with or without a slow pressor dose of Ang II via an osmotic minipump (0.5 mg/kg/day, i.p.), supplemented with a 2% NaCI diet or losartan, 20 mg/kg/day, for 2 weeks. Systolic (SBP), diastolic (DBP), and mean arterial blood (MAP) pressure were determined using the tail-cuff method, whereas 24 hr. urinary sodium and potassium excretion were determined using a metabolic cage. Serum and urine creatinine were measured using colorimetric assays, whereas glomerular and tubulointerstitial injury was evaluated by Masson’s Trichrome staining. Basal SBP levels were lower in PT- Sirt3 -/- than in WT mice (SBP-WT: 112 ± 2 vs. SBP-PT- Sirt3 -/- : 93 ± 2 mmHg, P &lt;0,01). The magnitude of Ang II-induced hypertension was similar between WT and PT- Sirt3 -/- mice with or without losartan treatment. Serum creatinine levels and urinary creatinine excretion were higher in PT- Sirt3 -/- mice than in WT mice ( P &lt;0.05), but without significant sex differences in response to Ang II infusion or losartan treatment. Differences were found only in female WT and PT- Sirt3 -/- mice with lower 24 hr. urine and urinary creatinine excretion in response to Ang II infusion or losartan. Losartan significantly increased 24 hr. urinary potassium and chloride excretion in Ang II-infused male and female PT- Sirt3 -/- mice ( P &lt;0.01). Finally, Ang II-infused PT- Sirt3 -/- mice showed significant renal cortical tubulointerstitial fibrotic responses ( P &lt;0.05), but not glomerular fibrotic responses. We conclude that basal blood pressure is lower in male and female PT- Sirt3 -/- mice and that Ang II induces similar hypertensive and renal fibrotic responses in male and female PT- Sirt3 -/- mice without significant sex differences.

Abstract P118: Angiotensin Ii Hypertension-dependent Decrease In Circadian Rhythms Of Cardiovascular Parameters: Role Of Peroxisome Proliferator Activated Receptor-α

Decreases in circadian rhythms of cardiovascular parameters, such as day to night changes in mean arterial pressure (MAP), heart rate (HR), pulse pressure (PP), systolic (SP) and diastolic pressure (DP) are an index of cardiovascular disease. Peroxisome proliferator activated receptor - alpha (PPAR-α) has been shown to decrease inflammatory markers and hypertension a slow pressor dose of Angiotensin II (Ang II); however, the role of PPAR-α on cardiovascular parameters during the initial stages of Ang II infusion is unknown. We hypothesize that the absence of PPAR-α will cause a reduction in the day to night changes in MAP, HR, PP, SP and DP during the initial stages of a slow pressor dose of Ang II. Male (10 - 12 weeks old) PPAR-αknockout (KO) and wild-type (WT) mice were infused with Ang II (400 ng/kg/min) for three days. Radiotelemetry was used to measure the cardiovascular parameters. The baseline MAP values were: 100 + 10 mmHg (WT) and 108 + 9 mmHg for KO. The baseline HR values were: 530 + 10 bpm (WT) and 526 + 6 bpm (KO). The baseline PPs were 17 + 0.2 mmHg (WT) and 18 + 0.3 mmHg (KO). The baseline SBPs were 108 + 9 mmHg (WT) and 116 + 10 mmHg (KO). The baseline DBPs were 91 + 9 mmHg (WT) and 98 + 10 mmHg (KO). During the first three days of Ang II infusion, the change in day to night MAP was 20 ± 2 mmHg and 10 ± 2 mmHg in Ang II treated WT and KO mice, respectively. Changes in day to night HR were 25 ± 4 bpm and 46 ± 7 bpm for WT and KO mice, respectively. The day to night changes in PP were 8 ± 1 mmHg for WT and 2 ± 2 mmHg for KO mice. The day to night changes in SBPs were 20 ± 2 mmHg and 12 ± 3 mmHg for WT and KO mice, respectively. Changes in day to night DBPs were 18 ± 2 mmHg for WT and 9 ± 2 mmHg for KO mice. TBARS and Interleukin-17 were increased in heart homogenates of KO + Ang II (15 ± 2 μM) and (1.5 ± 0.3 ng/mL) vs WT + Ang II (11 ± 3 μM) and (1.0 ± 0.2 ng/mL). Nitrite/Nitrate was decreased in KO + Ang II (1.0 ± 0.1 nM) vs WT + Ang II (1.5 ± 0.5 nM). In summary, the absence of PPAR-α decreases the day to night changes in MAP, SBP, DBP and PP during the initial three days of a slow pressor dose of Ang II. In the absence of PPAR-α, increases in oxidative stress and inflammation are mechanisms that may contribute to the changes in the cardiovascular parameters and suggest the occurrence of cardiovascular diseases during a slow pressor dose of Ang II-infusion.

Genetic Deletion of AT 1a Receptors Selectively in The Proximal Tubules of The Kidney Attenuates Angiotensin II‐induced Hypertensive and Glomerular Filtration Responses in Aging PT‐ Agtr1a ‐/‐ Mice

The intratubular renin-angiotensin system (RAS) via the angiotensinogen/renin/ACE/Ang II/AT1 (AT1a) receptor signaling pathways in the proximal tubules of the kidney play a critical role in the physiological regulation of blood pressure and the development of hypertension. Whether intratubular RAS continues to exert significant impacts on blood pressure and glomerular filtration responses to Ang II remains unknown. In the present study, we tested the hypothesis that deletion of AT1a receptors selectively in the proximal tubules of the kidney attenuates Ang II-induced hypertensive and glomerular filtration responses (GFR) in aging PT-Agtr1a-/- mice. To test the hypothesis, 6 groups (n=8-12 per group) of 20- to 24-month-old male wild-type (WT) and PT-Agtr1a-/- mice were infused with or without a slow pressor dose of Ang II (~0.65 mg/kg/day, i.p.), supplemented with a 2% Na+ diet for 2 weeks. Systolic blood pressure was determined by telemetry and tail-cuff techniques, whereas GFR was measured by the transdermal GFR monitoring technique with FITC-sinistrin, and the pressure-natriuresis responses was determined before and during Ang II infusion, respectively. Basal systolic blood pressure remained significantly lower in aging PT-Agtr1a-/- (104 ± 4 mmHg) than in aging WT mice (120 ± 4 mmHg, P<0.01), whereas basal GFR was significantly higher in aging PT-Agtr1a-/- mice (196.4 ± 14.7 µl/min) than in aging WT mice (142.6 ± 11.6 µl/min, P<0.01). Furthermore, the pressure-natriuresis response was significantly augmented in aging PT-Agtr1a-/-mice (P<0.05). Ang II infusion significantly induced hypertension (152 ± 3 mmHg, P<0.01) and decreased GFR in aging WT mice (122.4 ± 3.3 µl/min, P<0.01), as expected, but the hypertensive (135 ± 3 mmHg, P<0.01) and GFR responses were significantly improved in aging PT-Agtr1a-/-mice (155.9 ± 10.1 µl/min, P<0.01), respectively. Finally, proximal tubule-specific deletion of AT1a receptors significantly augmented the pressure-natriuresis response and natriuretic responses to Ang II infusion in aging PT-Agtr1a-/-mice (P<0.01). Taken together, the results of the present study suggest that intratubular Ang II and AT1a receptors in the proximal tubules continue to play a key role in the development of Ang II-induced hypertension in aging WT mice and that deletion of AT1a receptors selectively in the proximal tubules attenuates Ang II-induced hypertension and improves glomerular filtration in aging PT-Agtr1a-/- mice.

SEX DIFFERENCES IN ANGIOTENSIN II-INDUCED HYPERTENSION AND KIDNEY INJURY: ROLE OF AT1A RECEPTORS IN THE PROXIMAL TUBULE OF THE KIDNEY

Objective: Sex differences are widely recognized to play a critical role in cardiovascular, blood pressure and renal responses to the vasoactive peptide angiotensin II (Ang II) via activation of AT1 (AT1a) receptors. However, it is not known whether there are sex differences in the pressor and renal responses to Ang II in the absence of AT1a receptors in the proximal tubules of the kidney. In the present study, we tested the hypothesis that there are significant sex differences in Ang II-induced hypertension and kidney injury using male and female wild-type and proximal tubule-specific AT1a receptor knockout mice (PT-Agtr1a-/-). Design and method: To test our hypothesis, twelve groups (n = 8–12 per group) of adult male and female wild-type and PT-Agtr1a-/- mice were infused with a pressor dose of Ang II via osmotic pump for 2 weeks (1.5 mg/kg/day, i.p.) and simultaneously treated with or without losartan (20 mg/kg/day, p.o.) to determine the respective roles of AT1a receptors in extrarenal tissues or the proximal tubules of the kidney, respectively. Results: Minor sex differences were found in body wt., heart wt., or kidney wt. between male and female wild-type and PT-Agtr1a-/- mice. Basal systolic, diastolic, and mean arterial pressure were approximately 13 ± 3 mmHg lower (P &lt; 0.01), while basal 24 h urinary Na+, K+, and Cl- excretion were significantly higher in male and female PT-Agtr1a-/- mice than wild-type controls (P &lt; 0.01) without significant sex differences between different strains. Both male and female wild-type and PT-Agtr1a-/- mice developed time-dependent hypertension (P &lt; 0.01), and the magnitudes of the pressor responses to Ang II were similar between male and female wild-type and PT-Agtr1a-/- mice (n.s.). Likewise, Ang II-induced hypertension was significantly attenuated in male and female PT-Agtr1a-/- mice (P &lt; 0.01). Furthermore, losartan attenuated the hypertensive responses to Ang II to similar extents in male and female wild-type and PT-Agtr1a-/- mice. Finally, Ang II-induced kidney injury was attenuated in PT-Agtr1a-/- mice (P &lt; 0.01). Conclusions: In conclusion, the present study demonstrates that deletion of AT1a receptors in the proximal tubules of the kidney attenuates Ang II-induced hypertension and kidney injury without significant sex differences involved.

Less Invasive HeartMate 3 Left Ventricular Assist Device Implantation under Deep Hypothermic Circulatory Arrest for Severely Calcified Aorta

Introduction Left ventricular assist devices (LVADs) such as the HeartMate 3 (HM3) are becoming more frequently implanted in those with end-stage heart failure. We present one such patient with prior sternotomies and severely calcified ascending aorta in whom we planned a less invasive LVAD implantation via redo hemi-sternotomy and left thoracotomy with short-term deep hypothermic circulatory arrest (DHCA) to avoid cross-clamping of the aorta. Case Report A 70 year old male with history of two prior cardiac surgeries and heart failure presented in cardiogenic shock requiring temporary mechanical support with Impella CP. He continued to require increasing doses of inotropes and pressors; therefore, he was approved for high risk LVAD placement. A preoperative 4D CT scan revealed severely calcified ascending aorta with only a small area of focal sparing. First, a left anterior thoracotomy in the fifth intercostal space and redo upper hemi-sternotomy was performed. The LVAD outflow graft was positioned through the thoracotomy and brought up to the ascending aorta via the right pleural space, which was opened from the hemi-sternotomy. After initiation of cardiopulmonary bypass, the patient was cooled to 28°C with selective antegrade cerebral perfusion via the right axillary artery and systemic perfusion was temporarily arrested. DHCA was achieved. The LVAD outflow graft was then anastomosed to the aorta after which circulation was restarted and the patient rewarmed. The HM3 LVAD was then implanted in the LV apex and the rest of the operation was completed successfully. Summary Placing an LVAD via thoracotomy has theoretical advantages over a median sternotomy. Surgical trauma is minimized leading to less postoperative bleeding, improved maintenance of the chest stability, earlier recovery, and less cost. Additionally, there might be a reduction in post-operative right heart failure since the pericardium remains intact. Data from the LATERAL study and ELEVATE registry support the safety of this approach. While data support the safety of DHCA in other aortic arch procedures, there are only two case reports of DHCA for LVAD implantation. Our unique case validates the safety of LVAD implantation via thoracotomy and highlights the use of preoperative CT as well as DHCA in placement of an LVAD in a patient with severely calcified ascending aorta.