Acute Saline Research Articles

Kiosk 6R-FB-01 - Ventricular Extracellular Volume and Mass Changing Induced by Acute Saline Loading

Kiosk 6R-FB-01 - Ventricular Extracellular Volume and Mass Changing Induced by Acute Saline Loading

Delayed cognitive impairments in a rat model of Gulf War Illness are stimulus-dependent

Gulf War Illness (GWI) collectively describes the multitude of central and peripheral disturbances affecting soldiers who served in the 1990–1991 Gulf War. While the mechanisms responsible for GWI remain elusive, the prophylactic use of the reversible acetylcholinesterase inhibitor, pyridostigmine bromide (PB), and war-related stress have been identified as chief factors in GWI pathology. Post-deployment stress is a common challenge faced by veterans, and aberrant cholinergic and/or immune responses to these psychological stressors may play an important role in GWI pathology, especially the cognitive impairments experienced by many GWI patients. Therefore, the current study investigated if an immobilization stress challenge would produce abnormal responses in PB-treated rats three months later. Results indicate that hippocampal cholinergic responses to an immobilization stress challenge are impaired three months after PB administration. We also assessed if an immune or stress challenge reveals deficits in PB-treated animals during hippocampal-dependent learning and memory tasks at this delayed timepoint. Novel object recognition (NOR) testing paired with either acute saline or lipopolysaccharide (LPS, 30 µg/kg, i.p.), as well as Morris water maze (MWM) testing was conducted approximately three months after PB administration and/or repeated restraint stress. Rats with a history of PB treatment exhibited 24-hour hippocampal-dependent memory deficits when challenged with LPS, but not saline, in the NOR task. Similarly, in the same cohort, PB-treated rats showed 24-hour memory deficits in the MWM task. Ultimately, these studies highlight the long-term effects of PB treatment on hippocampal function and provide insight into the progressive cognitive deficits observed in veterans with GWI.

#4391 SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Abstract Background and Aims Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Method A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (P = .002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusion Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting.

SALT SENSITIVITY AND HYPERTENSIVE NEPHROPATHY: A LINK TO BE DISCOVERED

Objective: Sodium sensitivity is defined as a change in blood pressure depending on sodium intake, which is present in about 30% of the adult population. According to blood pressure variation in salt load test we can classify the population in 3 categories: sodium sensitive (SS), sodium resistant (SR), inverse sodium sensitivity (ISS), based on, respectively, an increase, a non-significant variation or a decrease in the blood pressure values following the administration of sodium. It is reported that SS subjects have, independently from other risk factors, an increased risk of cardiovascular diseases. Moreover, SNPs located in genes related with Na+ metabolism, aldosterone synthesis and tubular sodium reabsorption in the kidney are related to salt sensitivity phenotype. The aim of this study is to analyze the relationship between sodium sensitivity and the development of hypertensive kidney damage in patients with primary hypertension. Design and method: A cohort of 712 naïve hypertensive patients were classified for salt-sensitivity using acute saline test (NaCl 308 mEq / 2h / iv).127 patients (follow-up > 5 years- median 11) were selected for the present analysis (SS, n = 40; 0 SR, n = 46; RSS, n = 41). We analyzed annual decline of the eGFR (CDK-EPI) (Delta-eGFR) and development of microalbuminuria (MicrAlb) as renal outcome. Moreover, genetic polymorphism involved in salt sensitive hypertension has been investigated. Results: No differences in Delta-eGFR was observed among the groups. However, SR subjects develop earlier microalbuminuria (p = 0.002) even with an adequate pressure control. Genotypes analysis revealed: polymorphism in CYP11B2 and NEDD4L to be protective against decline in eGFR. For microalbuminuria HSD3B1 and ADD3 seem to be a risk factors, whereas KL, PKD and TRPC6 polymorphism result protective factors. Conclusions: Unexpectedly these finding suggests that SR patients are more at risk of developing hypertensive nephropathy than other groups of patients. Moreover genotypes associated with salt sensitivity play different and complex role in kidney damage in hypertension. Improvement in salt sensitivity testing and standardization will be needed to allow all this pathophysiological knowledge to be translated in a clinical setting

Inverse salt sensitivity: an independent risk factor for cardiovascular damage in essential hypertension.

Salt sensitivity is a powerful risk factor for cardiovascular (CV) disease and mortality in both normotensive and hypertensive patients. We investigated the predictive value of the salt sensitivity phenotype in the development of CV events and hypertensive target organ damage (TOD) among essential hypertensive patients. Eight hundred forty-four naive hypertensive patients were recruited and underwent an acute saline test during which blood pressure (BP) displayed either no substantial variation (salt-resistant, SR individuals), an increase (salt-sensitive, SS), or a paradoxical decrease (inverse salt-sensitive, ISS). Sixty-one patients with the longest monitored follow-up (median 16 years) for blood pressure and organ damage were selected for the present study. A clinical score for TOD development based on the severity and the age of onset was set up by considering hypertensive heart disease, cerebrovascular damage, microalbuminuria, and vascular events. CV events were significantly higher among SS and ISS than in SR patients. The relative risk of developing CV events was 12.67 times higher in SS than SR and 5.94 times higher in ISS than SR patients. The development of moderate to severe TOD was 10-fold higher in SS and over 15-fold higher in ISS than in SR patients. Among the three phenotypes, changes in plasma endogenous ouabain were linked with the blood pressure effects of saline. Salt sensitivity and inverse salt sensitivity appear to be equivalent risk factors for CV events. The response to an acute saline test is predictive of CV damage for newly identified ISS individuals.

Effects of Chronic and Acute Intranasal Oxytocin Treatments on Temporary Social Separation in Adult Titi Monkeys (Plecturocebus cupreus).

In socially monogamous titi monkeys, involuntary separation from a pair mate can produce behavioral distress and increased cortisol production. The neuropeptide oxytocin (OXT) is thought to play an important role in the separation response of pair-bonded species. Previous studies from our lab have shown that chronic intranasal oxytocin (IN OXT) during development can have long-term effects on adult social behavior. In the current study, we examined the chronic and acute effects of IN OXT or Saline (SAL) on the subjects’ response to a brief separation from their pair mates. Subjects with a history of chronic IN OXT or SAL treatment during development received a single dose of OXT or SAL as adults 30 min before being separated from their pair mate. Chronic treatment consisted of a daily dose of IN OXT (0.8 IU/kg) or SAL (control) from 12 to 18 months of age. Subjects (N = 29) were introduced to a pair mate at 30 months of age. After the pairs had cohabitated for 5 months, pairs underwent two “Brief Separation” (OXT and SAL) and two “Non-Separation” (OXT and SAL) test sessions. Vocalizations and locomotion were measured as behavioral indices of agitation or distress during the Brief Separation and Non-Separation periods (30 min each). We collected blood samples after the Brief Separation and Non-Separation periods to measure cortisol levels. Our results showed subjects treated with chronic OXT had a reduction in long call and peep vocalizations compared to subjects treated with chronic SAL. Subjects treated with chronic SAL and acute OXT produced more peeps and long calls compared to animals treated with acute SAL; however, patterns in this response depended on sex. Cortisol and locomotion were significantly higher during the Brief Separation period compared to the Non-Separation period; however, we did not find any treatment or sex effects. We conclude that chronic IN OXT given during development blunts the separation response, while acute OXT in chronic SAL subjects had sexually dimorphic effects, which could reflect increased partner seeking behaviors in males and increased anxiety in females.

Effects of Low Salinity on the Physiological Indices, Stress-Related Gene Expression, and Histological Changes in Phasolosma Esculenta

Acute saline stress can cause death of Phasolosma esculenta, an important aquaculture species in China. Hence, investigating the sensitivity and physiological responses of P. esculenta to saline stress is important. The molecular, physiological, and immune responses of the intestine and body wall of P. esculenta upon saline stress were investigated in this study. The mortality rate of P. esculenta increased with the decreasing salinity. The Na+/K+-ATPase and acid phosphatase activity peaked at 6 h and 12 h, respectively, in the intestine and body wall, and subsequently stabilized at a higher level than control group. Further, superoxide dismutase activity significantly decreased within 12 h and then increased slowly, while its genes expression decreased and reached its lowest level at 6 h. In the intestine and body wall of P. esculenta, saline stress induced the transcription of Heat Shock Protein-70, Heat Shock Protein-90, and ferritin, along with the enlargement and loosening of connective tissue cells. Moreover, saline stress induced a more prominent adaptive response in the intestine than body wall. This research indicated that the enzymatic system, nonenzymatic system, and gene expressions of P. esculenta changed under low saline stress and provided references for the further research on the low saline stress response in P. esculenta.

Quantifying preload alterations using a sensitive chest-mounted accelerometer

Abstract Seismocardiography (SCG) is a technology where the chest wall vibrations from the beating heart are measured using a highly sensitive accelerometer. SCG offers continuous measurement of cardiac function and potential applications include remote monitoring, diagnostic assessments, prognostic health checks and biventricular pacemaker optimization. Aim In the current study we examined how changes in preload influence SCG time intervals, by acute saline infusion. Methods We included twenty-six subjects, sixteen subjects with cardiac disease such as hypertrophic cardiomyopathy, dilated cardiomyopathy, aortic valve disease or ischemic heart disease (age 45.8±17.7 years and 93% male) and ten subjects without known cardiac conditions (age 42.1±14.4 years and 70% male). SCG was recorded from the xiphoid process using a custom-made sensor before and after acute infusion saline (median 2.0 L). The SCG signals were sampled with 5000 samples per second in 60 seconds, the individual heartbeats were identified using a dedicated segmentation algorithm and an average SCG beat was computed and used for the data analysis. Using a recently proposed nomenclature the following SCG fiducial points was identified: Es which coinciding with mitral valve closure, Gs which to some degree coincides with aortic opening, Bd coinciding with aortic valve closure and Fd coinciding with mitral valve opening [1]. The Es-Gs time interval was used as a measure of isovolumetric contraction time (IVCT), the Gs-Bd time interval was used as an estimate of ejection time (ET) and the Bd-Fd time interval as an estimate of isovolumetric relaxation time (IVRT). Paired t-test was used to test for significant response after infusion, while a two sample t-test was used to test for a significant difference in the observed response in subjects with or with our cardiac disease. Results For two subjects SCG after infusion was not obtained thus, twenty-four subjects were included in the final data analysis. In the whole group, acute saline infusion shortened the IVRT (Bd-Fd) from 91.0±15.3 ms to 82.7±15.3 ms (p=0.004) and prolonged the ET (Gs-Bd) from 329.4±35 ms to 343.4±33 ms (p<0.001). There was no significant change in IVCT (Es-Gs) which was 39.5±15.1 ms at baseline and 38.1±14.9 ms post-infusion (p=0.88). There was no significant difference in response between subjects with or without cardiac disease. Conclusion Increase in preload shortened the SCG time intervals related to the isovolumetric relaxation period and prolonged the period related to ejection time. SCG time intervals capture changes in preload, which demonstrates that the SCG is a potential modality for quantification of cardiac dynamics. Funding Acknowledgement Type of funding sources: None.

Quantifying preload alterations using a sensitive chest-mounted accelerometer

Abstract Seismocardiography (SCG) is a technology where the chest wall vibrations from the beating heart are measured using a highly sensitive accelerometer. SCG offers continuous measurement of cardiac function and potential applications include remote monitoring, diagnostic assessments, prognostic health checks and biventricular pacemaker optimization. Aim In the current study we examined how changes in preload influence SCG time intervals, by acute saline infusion. Methods We included twenty-six subjects, sixteen subjects with cardiac disease such as hypertrophic cardiomyopathy, dilated cardiomyopathy, aortic valve disease or ischemic heart disease (age 45.8±17.7 years and 93% male) and ten subjects without known cardiac conditions (age 42.1±14.4 years and 70% male). SCG was recorded from the xiphoid process using a custom-made sensor before and after acute infusion saline (median 2.0 L). The SCG signals were sampled with 5000 samples per second in 60 seconds, the individual heartbeats were identified using a dedicated segmentation algorithm and an average SCG beat was computed and used for the data analysis. Using a recently proposed nomenclature the following SCG fiducial points was identified: Es which coinciding with mitral valve closure, Gs which to some degree coincides with aortic opening, Bd coinciding with aortic valve closure and Fd coinciding with mitral valve opening [1]. The Es-Gs time interval was used as a measure of isovolumetric contraction time (IVCT), the Gs-Bd time interval was used as an estimate of ejection time (ET) and the Bd-Fd time interval as an estimate of isovolumetric relaxation time (IVRT). Paired t-test was used to test for significant response after infusion, while a two sample t-test was used to test for a significant difference in the observed response in subjects with or with our cardiac disease. Results For two subjects SCG after infusion was not obtained thus, twenty-four subjects were included in the final data analysis. In the whole group, acute saline infusion shortened the IVRT (Bd-Fd) from 91.0±15.3 ms to 82.7±15.3 ms (p=0.004) and prolonged the ET (Gs-Bd) from 329.4±35 ms to 343.4±33 ms (p<0.001). There was no significant change in IVCT (Es-Gs) which was 39.5±15.1 ms at baseline and 38.1±14.9 ms post-infusion (p=0.88). There was no significant difference in response between subjects with or without cardiac disease. Conclusion Increase in preload shortened the SCG time intervals related to the isovolumetric relaxation period and prolonged the period related to ejection time. SCG time intervals capture changes in preload, which demonstrates that the SCG is a potential modality for quantification of cardiac dynamics. Funding Acknowledgement Type of funding sources: None.

Effects of intravenous furosemide plus small-volume hypertonic saline solutions on markers of heart failure.

AimsWe sought to compare the effects of furosemide + hypertonic saline solution (HSS) treatment in patients with acute decompensated heart failure in comparison with furosemide alone and the response in a compensated state after an acute saline load with regard to serum levels of heart failure biomarkers.Methods and resultsWe enrolled 141 patients with acute decompensated heart failure with reduced ejection fraction admitted to our Internal Medicine ward from March 2017 to November 2019. A total of 73 patients were randomized to treatment with i.v. high‐dose furosemide plus HSS, whereas 68 patients were randomized to i.v. high‐dose furosemide alone. Patients treated with furosemide plus HSS compared with controls treated with furosemide alone showed a comparable degree of reduction in the serum levels of interleukin (IL)‐6, soluble suppression of tumorigenicity 2 (sST2), and N‐terminal pro‐brain natriuretic peptide (NT‐proBNP) in the ‘between‐group’ analysis. Nevertheless, patients treated with high‐dose furosemide + HSS showed significantly higher absolute delta values of IL‐6 (2.3 ± 1.2 vs. 1.7 ± 0.9, P < 0.0005, and 2.0 ± 0.8 vs. 1.85 ± 1.1, P = 0.034), sST2 (41.2 ± 8.6 vs. 27.9 ± 7.6, P < 0.0005, and 37.1 ± 6.6 vs. 28.4 ± 6.7, P < 0.0005), high‐sensitivity troponin T (0.03 ± 0.02 vs. 0.02 ± 0.01, P = 0.001, and 0.03 ± 0.02 vs. 0.02 ± 0.01, P = 0.009), NT‐proBNP (7237 ± 7931 vs. 3244 ± 4159, P < 0.005, and 5381 ± 4829 vs. 4466 ± 4332, P = 0.004), and galectin‐3 (15.7 ± 3.2 ng/mL vs. 11.68 ± 1.9 ng/mL, P < 0.0005, and 16.7 ± 3.9 ng/mL vs. 11.8 ± 2.4 ng/mL, P < 0.0005) than patients treated with furosemide alone. After acute saline load, patients treated with i.v. furosemide + HSS in comparison with subjects treated with furosemide alone showed a significantly lower increase in the serum concentrations of IL‐6 (−0.26 ± 0.42 pg/mL vs. −1.43 ± 0.86 pg/mL, P < 0.0005), high‐sensitivity troponin T (0 vs. −0.02 ± 0.02 ng/mL, P < 0.0005), sST2 (−8.5 ± 5.9 ng/mL vs. −14.6 ± 6.2 ng/mL, P < 0.0005), galectin‐3 (−2.1 ± 1.5 ng/mL vs. −7.1 ± 3.6 ng/mL, P < 0.0005), and NT‐proBNP (77 ± 1373 vs. −1706 ± 2259 pg/mL, P < 0.0005).ConclusionsOur findings concerning a comparable degree of reduction in the serum levels of three cardinal biomarkers indicate that a reduction in serum heart failure markers is not linked to the higher degree of congestion relief with a more rapid achievement of a clinical compensation state. This issue may have possible benefits on clinical practice concerning its therapeutic effects over and beyond the simple amelioration of clinical congestion signs and symptoms. Nevertheless, our findings of higher delta values after treatment with i.v. furosemide plus HSS indicate a possible higher efficacy by means of modulation of the stretching and fibrosis mechanisms.

Sequential Afferent‐Targeted and Total Renal Denervation and Impact on Regulation of Arterial Pressure, Glomerular Filtration, and Sodium Handling in Sprague Dawley Male Rats

Renal denervation (RDNx) is often reported to chronically decrease mean arterial pressure (MAP) in conscious, unchallenged Sprague Dawley (SD) rats, but has no effect of salt-sensitivity of MAP. Although these findings indicate an important role of renal nerves in long-term regulation of MAP under unchallenged conditions, the individual contributions of sympathetic and afferent renal nerves in MAP and renal homeostasis remain unclear. The present study was conducted to test the hypothesis that efferent (sympathetic) renal nerves are the primary contributors both MAP and renal function responses to RDNx in normotensive Sprague Dawley rats. To test this hypothesis, 12 adult male Sprague Dawley rats (300-325g) were subjected to sequential denervation procedures to ablate afferent and efferent nerves separately by subjecting rats to the following surgical sequence: Sham, then afferent-targeted RDNx (A-RDNx), then complete (T)-RDNx. A-RDNx was achieved by periaxonal application of 33mM capsaicin, and T-RDNx was achieved by surgical dissection followed by perivascular application of 10%(v/v) phenol in ethanol. One week was permitted for recovery from surgery before cardiovascular and renal measurements were collected. 24-hour mean arterial pressure (MAP) was recorded by implanted telemetry. Glomerular filtration rate (GFR) was assessed in unrestrained, conscious rats by acute FITC-sinistrin clearance. Renal excretory function was assessed by measuring the urinary sodium excretion response to an acute saline challenge (150mM PBS, 10% bodyweight, i.p.) over four hours. Data was analyzed by one-way repeated-measures ANOVA with Bonferroni post-hoc test (α=0.05). Data presented as mean±SEM. Sham surgery had no significant effect on MAP, GFR or Na Clearance. Following A-RDN treatment, MAP increased ∆5.4±0.9mmHg; (p<0.01); however, no significant changes in GFR or the excretory response to acute sodium load were detected. In contrast, following T-RDN, MAP was decreased 4.9±0.9mmHg (p<.01) following T-RDN vs. compared to A-RDN. Regarding renal function, GFR increased (1.20±0.05 vs. 1.06±0.04 mL/min/100gBWT; p<.01) as did the sodium excretory response to a saline load (28.2±2.3 vs. 18.6±1.0% Na load excreted per 4 hours; p<.01). Together, these data partly support our hypothesis and solidify the role for renal efferent (sympathetic) nerves contribute to long-term regulation of MAP, GFR, and sodium handling in the conscious SD rat. Contrary to our hypothesis, A-RDNx resulted in a small, yet significant, increase in MAP; however, no impact on renal function was observed. We speculate that the increased GFR and decrease in MAP are likely due to a decrease in renal vascular resistance and dilation of the renal afferent arterioles. Moreover, renal afferent nerves appear to contribute to maintenance of MAP in Sprague Dawley rats, which we speculate is through a tonic sympatho-inhibition due to the increase MAP following A-RDNx. These data highlight the important, yet differential roles of efferent and afferent renal nerves, and further studies are underway to further test this hypothesis.

PROXIMAL TUBULE-SPECIFIC DELETION OF AT1A RECEPTORS ATTENUATES ANGIOTENSIN II-INDUCED HYPERTENSION BY INCREASING GLOMERULAR FILTRATION AND THE PRESSURE-NATRIURESIS RESPONSE

Objective: The present study tested the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and full development of Ang II-induced hypertension. Design and method: Six groups (n = 7–12 per group) of adult male wild-type (WT) and PT-Agtr1a-/- mice were infused with or without Ang II for 2 weeks (1.5 mg/kg/day, i.p.). Glomerular filtration rate (GFR) was measued using fluorescein-labeled sinistrin, and natriuretic responses were determined under basal conditions and after Ang II infusion. Results: Basal systolic blood pressure were ∼13 ± 3 mmHg lower in PT-Agtr1a-/- than WT mice (P &lt; 0.01). However, basal GFR was higher in PT-Agtr1a-/- mice (WT: 160.4 ± 7.0 μl/min vs. PT-Agtr1a-/-: 186.0 ± 10 μl/min, P &lt; 0.01). Basal 24 h urinary Na+ excretion (UNaV) was higher in PT-Agtr1a-/- than WT mice (P &lt; 0.01). In response to Ang II infusion, both WT and PT-Agtr1a-/- mice developed hypertension with similar pressor response to Ang II in WT (43 ± 3 mmHg, P &lt; 0.01) and PT-Agtr1a-/- mice (39 ± 5 mmHg, P &lt; 0.01). However, systolic blood pressure was still 16 ± 3 mmHg lower in PT-Agtr1a-/- mice (P &lt; 0.01). Ang II decreased GFR to 132.2 ± 7.0 μl/min in WT mice (P &lt; 0.01), and to 129.4 ± 18.6 μl/min in PT-Agtr1a-/- mice (P &lt; 0.01), respectively. In WT mice, UNaV increased from 139.3 ± 22.3 μmol/24 h in the control group to 196.4 ± 29.6 μmol/24 h in the Ang II-infused group (P &lt; 0.01). In PT-Agtr1a-/- mice, UNaV increased from 172.0 ± 10.2 μmol/24 h in the control group to 264.7 ± 35.4 μmol/24 h in the Ang II-infused group (P &lt; 0.01). The pressor response to Ang II was attenuated, while the natriuretic response was augmented by losartan in WT and PT-Agtr1a-/- mice (P &lt; 0.01). Finally, proximal tubule-specific deletion of AT1a receptors significantly augmented the pressure-natriuresis response and natriuretic responses to acute saline infusion (P &lt; 0.01) or a 2% high salt diet for 2 weeks (P &lt; 0.01). Conclusions: The present study supports the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and the development of Ang II-induced hypertension.

Layer-Specific Strain Is Preload Dependent: Comparison between Speckle-Tracking Echocardiography and Cardiac Magnetic Resonance Feature-Tracking

Speckle-tracking echocardiographic (STE) imaging and cardiac magnetic resonance feature-tracking (CMR-FT) are novel imaging techniques enabling layer-specific quantification of myocardial deformation. Conventional echocardiographic parameters are load dependent, but few studies have investigated the effects of loading conditions on STE and CMR-FT layer-specific strain and the interchangeability of the two modalities. The aim of this study was to evaluate the effects of acute preload augmentation by saline infusion on STE and CMR-FT longitudinal and circumferential layer-specific strain parameters and their intermodal agreement. A total of 80 subjects, including 41 control subjects (mean age, 40±12years; 49% men) and 39 patients with cardiac disease (mean age, 47±15years; 92% men) were examined using STE and CMR-FT layer-specific strain analysis before and after saline infusion (median, 2.0L) with quantification of transmural global longitudinal strain (GLS), epicardial GLS, endocardial GLS, transmural global circumferential strain (GCS), epicardial GCS, and endocardial GCS in addition to epicardial-endocardial gradients. Bland-Altman plots and Pearson correlation coefficients were used to evaluate agreement between the two modalities across all strain parameters. Acute saline infusion increased all STE and CMR-FT layer-specific strain parameters in both groups. STE and CMR-FT GLS increased by 1.4±1.5% and 1.5±2.0% (P<.001) in control subjects and by 0.9±1.8% and 0.9±1.9% (P<.001) in patients with cardiac disease. STE and CMR-FT GCS increased by 2.0±2.2% and 1.8±2.3% (P<.001) in control subjects and by 1.8±2.3% and 1.7±3.6% in patients with cardiac disease (P<.001 and P=.03). STE longitudinal strain correlated strongly with corresponding CMR-FT longitudinal strain (GLS, epicardial GLS, and endocardial GLS: r=0.81, r=0.82, and r=0.81, respectively) despite poor intermodal agreement (bias±limits of agreement, -2.84±4.06%, 0.16±3.68%, and 2.33±3.52%, respectively) whereas GCS, epicardial GCS, and endocardial GCS correlated weakly between the two modalities (r=0.28, r=0.19, and r=0.34, respectively) and displayed poor intermodal agreement (bias±limits of agreement, -1.33±6.86%, 4.43±6.49%, and -9.92±8.55%, respectively). STE and CMR-FT longitudinal and circumferential layer-specific strain parameters are preload dependent in both control subjects and patients with cardiac disease. STE and CMR-FT longitudinal layer-specific strain parameters are strongly correlated, whereas circumferential layer-specific strain parameters are weakly correlated. STE and CMR-FT longitudinal and circumferential strain should not be used interchangeably, because of poor intermodal agreement.

Urinary proteomics reveals key markers of salt sensitivity in hypertensive patients during saline infusion.

Hypertension is a complex disease and is the major cause of cardiovascular complications. In the vast majority of individuals, the aetiology of elevated blood pressure (BP) cannot be determined, thus impairing optimized therapies and prognosis for individual patients. A more precise understanding of the molecular pathogenesis of hypertension remains a pressing priority for both basic and translational research. Here we investigated the effect of salt on naive hypertensive patients in order to better understand the salt intake-blood pressure relationship. Patients underwent an acute saline infusion and were defined as salt-sensitive or salt-resistant according to mean blood pressure changes. Urinary proteome changes during the salt load test were analysed by a label-free quantitative proteomics approach. Our data show that salt-sensitive patients display equal sodium reabsorption as salt-resistant patients, as major sodium transporters show the same behaviour during the salt load. However, salt-sensitive patients regulate the renin angiotensin system (RAS) differently from salt-resistant patients, and upregulate proteins, as epidermal growth factor (EGF) and plasminogen activator, urokinase (PLAU), involved in the regulation of epithelial sodium channel ENaC activity. Salt-sensitive and salt-resistant subjects have similar response to a saline/volume infusion as detected by urinary proteome. However, we identified glutamyl aminopeptidase (ENPEP), PLAU, EGF and Xaa-Pro aminopeptidase 2 precursor XPNPEP2 as key molecules of salt-sensitivity, through modulation of ENaC-dependent sodium reabsorption along the distal tubule.

Abstract P041: Proximal Tubule-specific Deletion Of Angiotensin Ii Type 1a Receptors In The Kidney Lowers Basal Blood Pressure And Attenuates Angiotensin Ii-induced Hypertension By Increasing Glomerular Filtration And The Pressure-natriuresis Response

The present study tested the hypothesis that intratubular angiotensin II (Ang II) and AT 1a receptors in the proximal tubules of the kidney plays an important role in basal blood pressure control and in the development of Ang II-induced hypertension. Mutant mice with proximal tubule-specific deletion of AT 1a receptors in the kidney, PT- Agtr1a -/- , were generated to test the hypothesis. Eight groups (n=7-12 per group) of adult male wild-type (WT) and PT- Agtr1a -/- mice were infused with or without Ang II for 2 weeks (1.5 mg/kg, i.p.). Basal systolic, diastolic, and mean arterial pressures were ~13 ± 3 mmHg lower in PT- Agtr1a -/- than WT mice ( P &lt;0.01). Basal glomerular filtration rate (GFR), as measured using transdermal FITC-sinistrin, was significantly higher in PT- Agtr1a -/- mice (WT: 160.4 ± 7.0 μl/min vs. PT- Agtr1a -/- : 186.0 ± 6.0 μl/min, P &lt;0.05). Basal 24 h urinary Na + excretion (U Na V) was significantly higher in PT- Agtr1a -/- than WT mice ( P &lt;0.01). In response to Ang II infusion, both WT and PT- Agtr1a -/- mice developed hypertension, and the magnitude of the pressor response to Ang II was similar in WT (Δ43 ± 3 mmHg, P &lt;0.01) and PT- Agtr1a -/- mice (Δ39 ± 5 mmHg, P &lt;0.01). However, the absolute blood pressure level was still 16 ± 3 mmHg lower in PT- Agtr1a -/- mice ( P &lt;0.01). Ang II significantly decreased GFR to 132.2 ± 7.0 μl/min in WT mice ( P &lt;0.01), and to 129.4 ± 18.6 μl/min in PT- Agtr1a -/- mice ( P &lt;0.01), respectively. In WT mice, U Na V increased from 139.3 ± 22.3 μmol/24 h in the control group to 196.4 ± 29.6 μmol/24 h in the Ang II-infused group ( P &lt;0.01). In PT- Agtr1a -/- mice, U Na V increased from 172.0 ± 10.2 μmol/24 h in the control group to 264.7 ± 35.4 μmol/24 h in the Ang II-infused group ( P &lt;0.01). The pressor response to Ang II was attenuated, while the natriuretic response was augmented by losartan in WT and PT- Agtr1a -/- mice ( P &lt;0.01). Finally, proximal tubule-specific deletion of AT 1a receptors significantly augmented the pressure-natriuresis response and natriuretic responses to acute saline infusion ( P &lt;0.01) or a 2% high salt diet ( P &lt;0.01). We concluded that deletion of AT 1a receptors selectively in the proximal tubules lowers basal blood pressure and attenuates Ang II-induced hypertension by increasing GFR and promoting the natriuretic response in PT- Agtr1a -/- mice.

Dietary Nitrate Counteracts The Elevated Blood Pressure Response To Nitric Oxide Synthase Inhibition In Humans

Decreased production of nitric oxide (NO) via the endogenous NO-synthase (NOS) pathway is a hallmark of impaired endothelial function and is associated with elevated blood pressure. Potentiation of the alternative nitrate-nitrite-NO pathway via the diet has been suggested as a possible therapeutic strategy to counteract NOS dysfunction, but proof-of-concept that exogenous nitrate treatment compensates in situations of NOS inhibition in humans is lacking. PURPOSE: To determine whether dietary supplementation with nitrate-rich beetroot juice attenuates the detrimental effects of acute NOS inhibition achieved by intravenous infusion of Nω-monomethyl-L-arginine (L-NMMA) on vascular function. METHODS: Seven male volunteers (age 23 ± 3 years, body mass 77.9 ± 6.8 kg) completed four conditions in a double-blind, randomised cross-over design: 1) 5-d dietary placebo supplementation with acute saline infusion (PL-CON), 2) 5-d placebo supplementation with acute L-NMMA infusion (3 mg/kgBM over 5 min followed by 55 μg/kgBM/min; PL-LNMMA), 3) 5-d dietary nitrate supplementation (12 mmol/d) with acute saline infusion (BR-CON), and 4) 5-d nitrate supplementation with acute L-NMMA infusion (BR-LNMMA). Heart rate (HR), brachial mean arterial pressure (MAP), and femoral artery blood flow (FBF) were measured every 5 min during 20 min of infusion and compared between conditions using repeated measures ANOVA. RESULTS: L-NMMA infusion resulted in decreases from baseline in HR (PL-LNMMA -5 ± 3, BR-LNMMA -6 ± 5 bpm) and FBF (PL-LNMMA -114 ± 85, BR-LNMMA -95 ± 71 mL/min) that were greater than after saline infusion (HR: PL-CON -2 ± 5, BR-CON -1 ± 4 bpm, P<0.05; FBF: 20 ± 40 and 18 ± 36 mL/min, P<0.05), with no effects of dietary supplementation. MAP was elevated by L-NMMA (PL-LNMMA 9 ± 2, BR-LNMMA 4 ± 2 mmHg) compared to saline infusion (PL-CON -2 ± 2, BR-CON 0 ± 2 mmHg, P<0.05), and this response was attenuated by ~56% following BR ingestion (P<0.05). CONCLUSIONS: Acute NOS blockade through systemic infusion of L-NMMA resulted in reduced HR and FBF, and elevated MAP, in healthy humans, resembling cardiovascular impairments observed in conditions of chronic NOS-dysfunction. BR attenuated the elevation in MAP, highlighting the potential for exogenous nitrate to improve vascular control in situations where NOS function is impaired.

Reduced genioglossus muscle activity caused by fluid overload in anesthetized rats.

IntroductionAlthough the precise cause of obstructive sleep apnea (OSA) remains unknown, various anatomical or structural factors are thought to influence upper airway patency. Recent clinical studies show that OSA is frequently observed among patients with fluid‐retaining states, such as heart/renal failure and postsurgery. It is important to note that a cause–effect relationship is not yet established, and our understanding of the effects of fluid overload is limited. The goal of this study was to investigate an animal model that can characterize the physiological changes that occur in response to fluid overload.MethodAcute nonsurvival experiments were conducted in 16 Sprague–Dawley rats. Rats were initially anesthetized by inhaled isoflurane, while the femoral vein was cannulated and urethane (1.2–1.5 g/Kg body weight) was gradually delivered intravenously to induce anesthesia. Additional doses of urethane were delivered as necessary to maintain a surgical plane of anesthesia. A surgical incision was made on the cervical area to catheterize carotid artery to measure blood pressure. A pair of stainless‐steel wires was injected into the tongue to measure genioglossus muscle activity (GGEMG). All physiological measurements were recorded as intravenous infusion of saline was provided to the rat (infusion rate = 22 ml/kg over 30 min).ResultsAcute saline overloading resulted in a 33% decrease in GGEMG, when compared to baseline. There was also a gradual drop in the respiratory rate (13% decrease) that reached statistical significance at 10 min after infusion was stopped. The blood pressure exhibited a 14% increase which subsequently returned to baseline within 40 min stopping infusion. There were no significant changes in the heart rate.ConclusionThe results of this study indicate that systemic fluid overload can affect significant changes in different physiological systems including reduction in genioglossus muscle activity, increase in blood pressure, and change autonomic nervous system function.

The synthetic cathinone 3,4-methylenedioxypyrovalerone increases impulsive action in rats.

A previous study from our laboratory has shown that the selective catecholamine reuptake inhibitor 3,4-methylenedioxypyrovalerone (MDPV) persistently alters impulsive choice as measured by delay discounting. To further understand the proimpulsive effects of MDPV, we examined its capacity to modulate a different impulsive measure - impulsive action - using a differential reinforcement of low rates of responding task with an inter-response time of 20 s. Three groups of male, Sprague-Dawley rats (n = 6) were first tested in daily sessions to understand the acute effects of cocaine (1.0-30.0 mg/kg), MDPV (0.1-3.0 mg/kg), or saline (1.0 ml/kg) on impulsive action. Both cocaine and MDPV increased impulsive action, most notably by decreasing timing error responses and response efficiency, but MDPV was more effective than cocaine. Additionally, MDPV suppressed operant responding in two of six animals at the highest dose tested. Next, the same animals received 10 postsession injections, once every other day, of either 30.0 mg/kg cocaine, 3.0 mg/kg MDPV, or 1.0 ml/kg saline based on their treatment group. An acute dose-effect redetermination was completed following the repeated administration studies, and once again MDPV and cocaine demonstrated proimpulsive effects. Interestingly, timing error responses were decreased in both MDPV and cocaine groups after an acute saline injection, potentially indicating persistent impulsive changes following the repeated administration phase of the experiment. These studies indicate that MDPV increases impulsive action acutely and that this increase may be potentiated following a series of repeated administrations.

The Deletion of AT1a Receptors Selectively in The Proximal Tubules of The Kidney Lowers Blood Pressure by Inducing Glomerular Hyperfiltration and Pressure‐Natriuresis Responses in PT‐Agtr1a−/− Mice

The renin‐angiotensin system (RAS) in the proximal tubules of the kidney plays a key role in the physiological regulation of proximal tubular Na+ reabsorption and normal blood pressure homeostasis. Inappropriate activation of intratubular RAS in the proximal tubules may contribute to angiotensin II (Ang II)‐induced hypertension. In the present study, we used proximal tubule‐specific knockout of AT1a receptors (PT‐Agtr1a−/−) in the kidney to test the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and full development of Ang II‐induced hypertension by altering glomerular filtration and the pressure‐natriuresis responses. To test the hypothesis, six groups (n=7–12 per group) of adult male wild‐type (WT) and PT‐Agtr1a−/− mice were infused with or without Ang II via osmotic minipump for 2 weeks (1.5 mg/kg, i.p.). Glomerular filtration rate (GFR) was monitored by an intradermal device using fluorescein‐labeled sinistrin, and natriuretic responses were determined under basal conditions and after Ang II infusion for 2 weeks. Basal systolic blood pressure were ~13 ± 3 mmHg lower in PT‐Agtr1a−/− than WT mice (P&lt;0.01). However, basal GFR was significantly higher in PT‐Agtr1a−/− mice (WT: 160.4 ± 7.0 μl/min vs. PT‐Agtr1a−/−: 186.0 ± 10 μl/min, P&lt;0.01). Basal 24 h urinary Na+ excretion (UNaV) was significantly higher in PT‐Agtr1a−/− than WT mice (P&lt;0.01). In response to Ang II infusion, both WT and PT‐Agtr1a−/− mice developed hypertension, and the magnitude of the pressor response to Ang II was similar in WT (Δ43 ± 3 mmHg, P&lt;0.01) and PT‐Agtr1a−/− mice (Δ39 ± 5 mmHg, P&lt;0.01). However, the absolute systolic blood pressure level was still 16 ± 3 mmHg lower in PT‐Agtr1a−/− mice (P&lt;0.01). Ang II significantly decreased GFR to 132.2 ± 7.0 μl/min in WT mice (P&lt;0.01), and to 129.4 ± 18.6 μl/min in PT‐Agtr1a−/− mice (P&lt;0.01), respectively. In WT mice, UNaV increased from 139.3 ± 22.3 μmol/24 h in the control group to 196.4 ± 29.6 μmol/24 h in the Ang II‐infused group (P&lt;0.01). In PT‐Agtr1a−/− mice, UNaV increased from 172.0 ± 10.2 μmol/24 h in the control group to 264.7 ± 35.4 μmol/24 h in the Ang II‐infused group (P&lt;0.01). The pressor response to Ang II was attenuated, while the natriuretic response was augmented by losartan in WT and PT‐Agtr1a−/− mice (P&lt;0.01). Finally, proximal tubule‐specific deletion of AT1a receptors significantly augmented the pressure‐natriuresis response and natriuretic responses to acute saline infusion (P&lt;0.01) or a 2% high salt diet for 2 weeks (P&lt;0.01). In conclusion, the present study supports the hypothesis that Ang II and AT1a receptors in the proximal tubules are required for normal blood pressure homeostasis and the full development of Ang II‐induced hypertension, and suggest that deletion of AT1a receptors selectively in the proximal tubules lowers basal blood pressure by inducing glomerular hyperfiltration and promoting the natriuretic response in PT‐Agtr1a−/− mice.Support or Funding InformationThis work was supported in part by NIDDK grants, 2R01DK067299‐06A2, 2R01DK067299‐10A1, 5R01DK102429‐01, and 2R01DK102429‐03A1 to Dr. Zhuo.

Cardiac Versus Renal Response to Volume Expansion in Preclinical Systolic Dysfunction With PDEV Inhibition and BNP

Impaired cardiorenal response to acute saline volume expansion in preclinical systolic dysfunction (PSD) may lead to symptomatic heart failure. The objective was to determine if combination phosphodiesterase-V inhibition and exogenous B-type natriuretic peptide (BNP) administration may enhance cardiorenal response. A randomized double-blinded, placebo-controlled study was conducted in 21 subjects with PSD and renal dysfunction. Pre-treatment with tadalafil and subcutaneous BNP resulted in improved cardiac function, as evidenced by improvement in ejection fraction, left atrial volume index, and left ventricular end-diastolic volume. However, there was reduced renal response with reduction in renal plasma flow, glomerular filtration rate, and urine flow. (Tadalafil and Nesiritide as Therapy in Pre-clinical HeartFailure; NCT01544998).