2K1C Rats Research Articles

Fenofibrate Attenuates Hypertension in Goldblatt Hypertensive Rats: Role of 20-Hydroxyeicosatetraenoic Acid in the Nonclipped Kidney

BackgroundThere is vast evidence that the renin-angiotensin system is not the sole determinant of blood pressure (BP) elevation in human renovascular hypertension or the relevant experimental models. This study tested the hypothesis that kidney deficiency of 20-hydroxyeicosatetraenoic acid (20-HETE), a product of cytochrome P450 (CYP)-dependent ω-hydroxylase pathway of arachidonic acid metabolism, is important in the pathophysiology of the maintenance phase of 2-kidney, 1-clip (2K1C) Goldblatt hypertension. Materials and MethodsIn 2K1C Goldblatt rats with established hypertension, angiotensin II, angiotensin 1-7, 20-HETE concentrations and gene expression of CYP4A1 enzyme (responsible for 20-HETE formation) of the nonclipped kidney were determined. We examined if 14 days׳ administration of fenofibrate, a lipid-lowering drug, would increase CYP4A1 gene expression and renal 20-HETE formation, and if increased 20-HETE concentrations in the nonclipped kidney would decrease BP (telemetric measurements). ResultsCYP4A1 gene expression, 20-HETE and angiotensin 1-7 concentrations were lower and angiotensin II levels were higher in the nonclipped kidney of 2K1C rats than in sham-operated rats. Fenofibrate increased CYP4A1 gene expression and 20-HETE concentration in the nonclipped kidney and significantly decreased BP in 2K1C rats but did not restore it to normotensive range. The treatment did not change BP in sham-operated rats. ConclusionsOur results suggest that alterations in the RAS and CYP-dependent ω-hydroxylase metabolites of arachidonic acid in the nonclipped kidneys are both important in the pathophysiology of the maintenance phase of 2K1C Goldblatt hypertension. Therefore, fenofibrate treatment effectively attenuated hypertension, probably via stimulation of 20-HETE formation in the nonclipped kidney.

Protective Cardiorenal Effects Of Tropaeolum majus L. In Rats With Renovascular Hypertension

: Background: Tropaeolum majus L. (Tropaeolaceae) is an important medicinal plant belonging to the Tropaeolaceae family, which has 80 species distributed in South and Central America. In Brazil, it is distributed practically throughout the entire territory and it is popularly known as “capuchinha”. In folk medicine its leaves are widely used for treatment of cardiovascular disorders. Despite consistent data showing some acute effects on renal and cardiovascular system, no study has investigated whether Tropaeolum majus extracts is able to exert cardiorenal protective effects after 30 days of treatment, i.e. in a sustained manner. Objective: Investigate the prolonged cardiorenal protective effects of ethanolic extract obtained from Tropaeolum majus (EETM) in rats with renovascular hypertension. Material and Methods: First, EETM was obtained and chemically characterized. Then, we investigated the possible antihypertensive and diuretics effects, including effects on renal haemodynamics, after prolonged treatment (30 days) with EETM (3, 30 and 300 mg/kg). Finally, we examined whether treatment with EETM may affect the angiotensin-converting enzyme (ACE) and oxidative stress, preventing heart and kidney damage in two-kidney, one-clip (2K1C) Goldblatt hypertensive rats. Results: Prolonged treatment with EETM was able to prevent the evolution of renovascular hypertension in 2K1C rats, inducing important renoprotective effects and reducing systemic blood pressure and cardiac hypertrophy. Moreover, it was also identified that these effects may be directly related to significant ACE inhibitory activity and reduction of oxidative stress. Conclusion: This study has brought new scientific evidence of preclinical efficacy of EETM as a cardiorenal protective agent in rats with renovascular hypertension.Key words: Antihypertensive, Cardioprotective, Diuretic, Renoprotective, Tropaeolum majus L.

Transplantation of bone marrow-derived MSCs improves renal function and Na++K+-ATPase activity in rats with renovascular hypertension.

Renovascular hypertension (RVH) is a progressive disease, leading to chronic kidney disease when untreated and no specific treatment is available. Therefore, development of new therapeutic modalities is imperative. RVH is triggered by renal artery stenosis and subsequent renin-angiotensin-aldosterone system activation; it can be experimentally induced by the 2 Kidneys-1 Clip (2K1C) model. This study investigates the therapeutic potential of renal subcapsular mesenchymal stem cell (MSC) infusion in 2K1C rats. Renal morphological and functional changes were analyzed, including Na++K+-ATPase activity and expression, renin angiotensin-converting enzyme (ACE) and angiotensin-II type 1 (AT1R) and type 2 (AT2R) receptors expression. 2K1C rats developed hypertension accompanied by renin upregulation (clipped kidney) and renal Na++K+-ATPase activity and expression reduction. MSC therapy decreased systolic blood pressure, renin, ACE, and AT1R, upregulated AT2R and podocin expression and restored renal Na++K+-ATPase activity and expression. In addition, MSC improved renal morphology, reduced fibrosis and TGF-β expression in the clipped kidney, decreased proteinuria and restored protein plasma levels. In conclusion, transplantation into a renal subcapsule is an efficient route and MSC is a good candidate for cell therapy, which may represent an interesting approach for chronic kidney disease treatment.

The differential effects of low and high doses of apelin through opioid receptors on the blood pressure of rats with renovascular hypertension.

The apelin/APJ system has an important role in the regulation of vascular tone and blood pressure. Opioid receptors (OPRs) are also important cardiovascular regulators and exert many of their effects by modulating the function of other G-protein-coupled receptors. The aim of this study was to analyze the interaction of apelin and the opioid system with respect to vascular responses to apelin in rats with renovascular hypertension (two-kidney, one clip (2K1C)). Homodynamic studies were carried out in 2K1C rats. Naloxone (a nonselective OPR inhibitor) or nor-binaltorphimine dihydrochloride (norBNI, a kappa OPR inhibitor) and signaling pathway inhibitors PTX (a Gi path inhibitor) and chelerythrine (a protein kinase C (PKC) inhibitor) were administered before apelin at 20 and 40 μg kg-1. Apelin at 20 and 40 μg kg-1 decreased the systolic blood pressure by 15% and 20%, respectively (P<0.05). The pressure drop caused by apelin 20 was inhibited by naloxone, norBNI and PTX, but it was not affected by chelerythrine. The pressure drop caused by apelin 40 was augmented by naloxone and chelerythrine, and it was not affected by norBNI or PTX. The lowering effect of apelin 20 on blood pressure is exerted through OPRs and stimulation of Gi and PKC pathways. However, apelin 40 functions independently of OPRs, Gi and PKC. This dose-dependent differential effect of apelin may have potential clinical applications as opioids are currently used, and apelin has been introduced as a potential therapeutic agent in cardiovascular complications.

Increased Expression of Macrophage Migration Inhibitory Factor in the Nucleus of the Solitary Tract Attenuates Renovascular Hypertension in Rats.

Macrophage migration inhibitory factor (MIF) is an intracellular inhibitory regulator of the actions of angiotensin II in the central nervous system. Renovascular hypertensive 2-kidney, 1-clip (2K1C) rats have an increased activity of the renin-angiotensin system and a decrease in baroreflex function compared to normotensive (NT) rats. In the present study, we tested the effects of MIF overexpression within the nucleus of the solitary tract (NTS), a key brainstem region for cardiovascular regulation, on the development of hypertension, on baroreflex function, and on water and food intake in 2K1C rats. Holtzman NT rats received a silver clip around the left renal artery to induce 2K1C hypertension. Three weeks later, rats were microinjected in the NTS with AAV2-CBA-MIF, to increase the expression of MIF, or with the control vector AAV2-CBA-enhanced green fluorescent protein. Mean arterial pressure (MAP) and heart rate were recorded by telemetry. Baroreflex function was tested, and water and food intake were also measured. Increasing MIF expression in the NTS of 2K1C rats attenuated the development of hypertension, reversed the impairment of baroreflex function, and reduced the increase in water intake. In contrast to 2K1C rats, similar increases in MIF expression in the NTS of NT rats produced no changes in baseline MAP, baroreflex function, or water intake. These results indicate that an increased expression of MIF within the NTS attenuates the development of hypertension and restores the baroreflex function in 2K1C rats.

Ruthenium Complex Improves the Endothelial Function in Aortic Rings From Hypertensive Rats.

BackgroundThe endothelium is a monolayer of cells that extends on the vascular inner surface, responsible for the modulation of vascular tone. By means of the release of nitric oxide (NO), the endothelium has an important protective function against cardiovascular diseases.ObjectiveVerify if cis- [Ru(bpy)2(NO2)(NO)](PF6)2 (BPY) improves endothelial function and the sensibility of conductance (aorta) and resistance (coronary) to vascular relaxation induced by BPY.MethodsNormotensive (2K) and hypertensive (2K-1C) Wistar rats were used. For vascular reactivity study, thoracic aortas were isolated, rings with intact endothelium were incubated with: BPY(0.01 to10 µM) and concentration effect curves to acetylcholine were performed. In addition, cumulative concentration curves were performed to BPY (1.0 nM to 0.1 µM) in aortic and coronary rings, with intact and denuded endothelium.ResultsIn aorta from 2K-1C animals, the treatment with BPY 0.1µM increased the potency of acetylcholine-induced relaxation and it was able to revert the endothelial dysfunction. The presence of the endothelium did not modify the effect of BPY in inducing the relaxation in aortas from 2K and 2K-1C rats. In coronary, the endothelium potentiated the vasodilator effect of BPY in vessels from 2K and 2K-1C rats.ConclusionOur results suggest that 0.1 µM of BPY is able to normalize the relaxation endothelium dependent in hypertensive rats, and the compound BPY induces relaxation in aortic from normotensive and hypertensive rats with the same potency. The endothelium potentiate the relaxation effect induced by BPY in coronary from normotensive and hypertensive rats, with lower effect on coronary from hypertensive rats.

The Effects of Aqueous Extract from Nardostachys chinensis Batalin on Blood Pressure and Cardiac Hypertrophy in Two‐Kidney One‐Clip Hypertensive Rats

Aims The aim of this study was to investigate the effects of the aqueous extract of Nardostachys chinensis Batalin (NCBAE) on blood pressure and cardiac hypertrophy using two-kidney one-clip (2K1C) hypertensive rats. Methods 2K1C rat models were set up by clipping the left renal artery. Sham-operated rats underwent the same surgical procedure except for renal arterial clipping. 2K1C hypertensive rats were orally given NCBAE at doses of 210, 420, and 630 mg·kg−1·d−1 for 6 weeks. Twelve weeks after surgery, rat SBP and echocardiographic parameters were measured, cardiac histopathology was assessed, serum NO and LDH were detected, and the expression of Bcl-2 and caspase-3 of left ventricular tissue was assessed by western blot. Results Treatment with NCBAE resulted in a decrease of SBP, LVPWd, LVPWs, IVSd, IVSs, LVW/BW ratio, and cardiomyocyte CSA, an increase of LVEF, and inhibition of 2K1C-induced reduction in serum NO and elevation of LDH compared with 2K1C group. NCBAE intervention also showed a significant increase of Bcl-2 expression and reduction of cleaved caspase-3 level dose-dependently in left ventricular tissue. Conclusion Our data demonstrate that NCBAE has an antihypertensive property and protective effect on 2K1C-induced cardiac hypertrophy especially at the dose of 630 mg·kg−1·d−1.

Exercise training attenuates renovascular hypertension partly via RAS- ROS- glutamate pathway in the hypothalamic paraventricular nucleus.

Exercise training (ExT) has been reported to benefit hypertension; however, the exact mechanisms involved are unclear. We hypothesized that ExT attenuates hypertension, in part, through the renin-angiotensin system (RAS), reactive oxygen species (ROS), and glutamate in the paraventricular nucleus (PVN). Two-kidney, one-clip (2K1C) renovascular hypertensive rats were assigned to sedentary (Sed) or treadmill running groups for eight weeks. Dizocilpine (MK801), a glutamate receptor blocker, or losartan (Los), an angiotensin II type1 receptor (AT1-R) blocker, were microinjected into the PVN at the end of the experiment. We found that 2K1C rats had higher mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA). These rats also had excessive oxidative stress and overactivated RAS in PVN. Eight weeks of ExT significantly decreased MAP and RSNA in 2K1C hypertensive rats. ExT inhibited angiotensin-converting enzyme (ACE), AT1-R, and glutamate in the PVN, and angiotensin II (ANG II) in the plasma. Moreover, ExT attenuated ROS by augmenting copper/zinc superoxide dismutase (Cu/Zn-SOD) and decreasing p47phox and gp91phox in the PVN. MK801or Los significantly decreased blood pressure in rats. Together, these findings suggest that the beneficial effects of ExT on renovascular hypertension may be, in part, through the RAS-ROS-glutamate pathway in the PVN.

Hypotensive effect and vascular relaxation in different arteries induced by the nitric oxide donor RuBPY

NO donors are compounds that release NO that can be used when the endogenous NO bioavailability is impaired. The compound cis-[Ru(bpy)2(py)(NO2)](PF6) (RuBPY) is a nitrite-ruthenium, since it has a NO2 in its molecule. The aim of the present study was to evaluate the effect of RuBPY on arterial pressure, as well as on the vascular relaxation of different vascular arteries in renal hypertensive (2K-1C) and normotensive (2K) rats. We have evaluated the arterial pressure and heart rate changes as well as the RuBPY and SNP-induced relaxation (thoracic aorta, mesenteric resistance, coronary and basilar arteries). The administration of RuBPY in awake rats evoked a smaller but long lasting hypotensive effect when compared to SNP, with no increase in heart rate. The relaxation induced by RuBPY was similar between 2K-1C and 2K rats in thoracic aorta, mesenteric resistance and coronary arteries. However, the relaxation induced by RuBPY was smaller in basilar arteries from 2K-1C than in 2K. Taken together, our results show that RuBPY presents several advantages over SNP, since it does not induce hypotensive effect in normotensive animals, the hypotensive effect is slower, with no reflex tachycardia, and it is long lasting. In addition, RuBPY induces coronary artery relaxation (useful for angina) and presented only a small effect on basilar artery (may not induce headache).

Renal sympathetic denervation attenuates hypertension and vascular remodeling in renovascular hypertensive rats.

The effects of renal sympathetic denervation (RSD) on hypertension, cardiac function, vascular fibrosis, and renal apoptosis were studied in the 2K1C rat model. Results showed that RSD attenuated hypertension, improved vascular remodeling, and reduced vascular fibrosis through decreased sympathetic activity in the 2K1C rat model, but it did not change the kidney size, renal apoptosis, or renal caspase-3 expression. These results could suggest possible clinical efficacy of RSD for renovascular hypertension.

Carotid sinus denervation ameliorates renovascular hypertension in adult Wistar rats.

Peripheral chemoreflex sensitization is a feature of renovascular hypertension. Carotid sinus nerve denervation (CSD) has recently been shown to relieve hypertension and reduce sympathetic activity in other rat models of hypertension. We show that CSD in renovascular hypertension halts further increases in blood pressure. Possible mechanisms include improvements in baroreceptor reflex sensitivity and renal function, restoration of cardiac calcium signalling towards control levels, and reduced neural inflammation. Our data suggest that the peripheral chemoreflex may be a viable therapeutic target for renovascular hypertension. The peripheral chemoreflex is known to be hyper-responsive in both spontaneously hypertensive (SHR) and Goldblatt hypertensive (two kidney one clip; 2K1C) rats. We have previously shown that carotid sinus nerve denervation (CSD) reduces arterial blood pressure (ABP) in SHR. In the present study, we show that CSD ameliorates 2K1C hypertension and reveal the potential underlying mechanisms. Adult Wistar rats were instrumented to record ABP via telemetry, and then underwent CSD (n=9) or sham CSD (n=9) 5weeks after renal artery clipping, in comparison with normal Wistar rats (n=5). After 21days, renal function was assessed, and tissue was collected to assess sympathetic postganglionic intracellular calcium transients ([Ca2+ ]i ) and immune cell infiltrates. Hypertensive 2K1C rats showed a profound elevation in ABP (Wistar: 98±4mmHg vs. 2K1C: 147±8mmHg; P<0.001), coupled with impairments in renal function and baroreflex sensitivity, increased neuroinflammatory markers and enhanced [Ca2+ ]I in stellate neurons (P<0.05). CSD reduced ABP in 2K1C+CSD rats and prevented the further progressive increase in ABP seen in 2K1C+sham CSD rats, with a between-group difference of 14±2mmHg by week 3 (P<0.01), which was accompanied by improvements in both baroreflex control and spectral indicators of cardiac sympatho-vagal balance. Furthermore, CSD improved protein and albuminuria, decreased [Ca2+ ]i evoked responses from stellate neurons, and also reduced indicators of brainstem inflammation. In summary, CSD in 2K1C rats reduces the hypertensive burden and improves renal function. This may be mediated by improvements in autonomic balance, functional remodelling of post-ganglionic neurons and reduced inflammation. Our results suggest that the peripheral chemoreflex may be considered as a potential therapeutic target for controlling renovascular hypertension.

Renovascular hypertension: Effects of mesenchymal stem cells in the contralateral hypertensive kidney in rats

ABSTRACTMesenchymal stem cells (MSC) induced neovascularization and improved renal morphology of the stenotic kidney in 2 kidneys-1 clip (2K-1C) model of renovascular hypertension. The present study evaluated the effects of MSC in the contralateral hypertensive kidney. Three weeks after left renal artery occlusion, MSC were injected into the tail vein of the 2K-1C rats. Renal function and morphology were analyzed in both kidneys. Labeled MSC were found in stenotic and contralateral kidneys. Hypertensive 2K-1C animals presented increased circulating levels of Angiotensin II (Ang II) and renin. MSC prevented the progressive increase of blood pressure and reduced circulating Ang II and renin levels. Stenotic kidney showed reduced renal plasma flow (RPF) and glomerular filtration rate (GFR), whereas the contralateral kidney had a tendency (p > 0.5) of reduction in GFR in spite of unchanged RPF. MSC treatment caused an improvement in GFR with no effect of on RPF in the stenotic kidney. Contralateral kidney showed increased diuresis and natriuresis that were even higher in MSC-treated animals, indicating that cell treatment improved the capacity of the contralateral kidney to excrete sodium. Contralateral kidney expressed higher levels of inflammatory cytokines (IL-6, TNF-α) and signs of fibrosis, which were attenuated by MSC treatment. MSC treatment improved the stenotic kidney function, and it was also beneficial to the contralateral hypertensive kidney because it improved the morphology and preserved its capacity to excrete sodium.

Increased Dietary Salt Changes Baroreceptor Sensitivity and Intrarenal Renin-Angiotensin System in Goldblatt Hypertension.

Renovascular hypertension (2-kidney 1-clip model (2K1C)) is characterized by renin-angiotensin system (RAS) activation. Increased Angiotensin II (AngII) leads to sympathoexcitation, oxidative stress, and alterations in sodium and water balance. The aim of this study was to evaluate whether a discrete increase in sodium chloride intake in 2K1C rats leads to changes in cardiovascular and autonomic function, oxidative stress, and renin angiotensin aldosterone system. After 4 weeks of induction of hypertension, rats were fed a normal sodium diet (0.4% NaCl) or a high-sodium diet (2% NaCl) for 2 consecutive weeks. Experiments were carried out for 6 weeks after clipping. Mean arterial pressure (MAP), renal sympathetic nerve activity (rSNA), arterial baroreflex control of rSNA, and heart rate (HR) were assessed. Thiobarbituric acid reactive substances and glutathione were measured as indicators of systemic oxidative stress. Angiostensin-converting enzyme (ACE), ACE2, and angiotensinogen were evaluated in clipped and unclipped kidneys as also urinary angiotensinogen and plasma renin activity. Angiotensinogen, plasma renin activity (PRA) and angiotensin-converting enzyme (ACE) and ACE2 in clipped and unclipped kidneys were evaluated. High-sodium diet did not change systemic oxidative stress, and basal values of MAP, HR, or rSNA; however, increased renal (-0.7±0.2 vs. -1.5±0.1 spikes/s/mm Hg) and cardiac (-0.9±0.14 vs. -1.5±0.14 bpm/mm Hg) baroreceptor reflex sensitivity in 2K1C rats. Although there was no alteration in PRA, a high-salt diet significantly decreased urinary angiotensinogen, ACE, and ACE2 expressions in the clipped and unclipped kidneys. Increased arterial baroreceptor control associated with a suppression of the intrarenal RAS in the 2K1C rats on high-salt diet provide a salt-resistant effect on hypertension and sympathoexcitation in renovascular hypertensive rats.

Hydrogen Sulfide Improves Myocardial Remodeling via Downregulated Angiotensin Ⅱ/AT1R Pathway in Renovascular Hypertensive Rats

Hydrogen sulfide (H2S) is an important endogenous gaseous transmitter in many physiological functions. Plasma H2S decreased, and angiotensin II (Ang II) type 1 receptor (AT1R) increased in the myocardial tissues in 2-kidney 1-clip (2K1C) rats than in normotensive rats. Accumulating evidences suggest that H2S inhibited Ang II/AT1R pathway to regulate cardiovascular function. Therefore, we hypothesized that H2S may exert beneficial effects on myocardial remodeling in 2K1C rat models of renovascular hypertension. Sodium hydrosulfide (NaHS, 56 µmol/kg/day) was administered intraperitoneally to the rats from the 7th day after 2K1C operation. Systolic blood pressure was significantly increased from the first week after the operation and was lowered after NaHS treatment for 4 weeks. H2S could also inhibit the ratio of left ventricle and septum weight to body weight, improve cross-sectional area, and ameliorate ventricular dysfunction. Additionally, the protein expression of AT1R and Ang II serum content were downregulated, whereas superoxide dismutase (SOD) protein was upregulated in 2K1C rats by NaHS treatment for 4 weeks. Furthermore, the reactive oxygen species level and AT1R protein were increased, whereas SOD protein was decreased in cardiomyocytes treated with Ang II compared with the control group. NaHS could reverse these changes. Losartan and N-acetylcysteine could also reverse Ang II-induced changes. The protective effect of H2S is attributable to the suppression of oxidative stress. This process involves the inhibition of the Ang II/AT1R pathway and upregulation of antioxidant enzymes in 2K1C rats.

Abstract P609: Saccharina Japonica Soaked In Vinegar Remarkably Decreased Blood Pressure In 2-kidney, 1-clip Renovascular Hypertensive Rats.

Objective: One of foods indispensable to Japanese cuisine “Washoku” is algae, including Saccharina japonica (SJ) and Undaria pinnatifida. The intake of SJ is reported to decrease blood pressure (BP) in spontaneously hypertensive rats in some studies, and in 2-kidney, 1-clip hypertensive (2K1C) rats in our studies. Since SJ soaked in vinegar is often used in Japanese cuisine, we observed the effects of dietary intake of SJ soaked in vinegar on BP in 2K1C rats. Methods: Male Sprague-Dawley rats (6 wks) were treated with sham operation (SHAM) or clipping the left renal artery (2K1C). After surgery, the rats started receiving a control diet (C), a diet with 5.0% (w/w) SJ (S), or a diet with 5.0% SJ soaked in 5.0% (v/v) vinegar (SV). Systolic BP (SBP) was measured by a tail-cuff method every week for 6 weeks. At the end of the protocol, mean arterial BP (MAP) was measured in each rat under anesthesia. Results and Discussion: Analysis of variance shows that SBP was significantly higher in 2K1C-C than SHAM-C through the experimental period (P&lt;0.001), and that SBP was lower in 2K1C-S (P&lt;0.05) and -SV (P&lt;0.001) than in 2K1C-C (Fig). It also demonstrated that 2K1C-SV provided a significant reduction in SBP compared with 2K1C-S (p&lt;0.001). At the end of the protocol, MAP in 2K1C-C was significantly higher than SHAM-C (154±4 vs 141±4 mmHg, P&lt;0.05). Compared with 2K1C-C, a significant reduction in MAP was observed not in 2K1C-S (143±2 mmHg) but in 2K1C-SV (133±4 mmHg, p&lt;0.05). Soaking in vinegar might bring alginate, which is one of possible components playing an important role in decreasing BP by SJ, to a low molecule and enhance the effect. Conclusion: SJ soaked in vinegar may decrease BP more than SJ in 2K1C rats.

OS 15-06 SEQUENTIAL ACTIVATION OF INTRARENAL ACE/ACE2 AS THE PROGRESSION OF HYPERTENSIVE NEPHROPATHY IN 2-KIDNEY 10CLIP (2K1C) GOLDBLATT RATS

Objective: Intrarenal renin-angiotensin system (RAS) had an important role to generate and maintain hypertension in 2-kidny 1-clip (2K1C) rats. This study purposed to assess how various intrarenal RAS components of 2K1C rats contributed to hypertension in different parts (cortex, medulla) of both sides (CK; clipped-kidney, NCK; non-clipped kidney) at different times (2 weeks; 2w and 5 weeks; 5w after clipping operation). Design and Method: We conducted to insert clip to left renal artery or sham operation to SD rats, then systolic blood pressure (SBP) was measured at one week interval. Kidney tissues were prepared for molecular and pathologic analysis in 2w and 5w after operation. Results: SBP increased in 2K1C rats within 1 week followed by clipping operation. At 2 w, juxtaglomerular apparatus (JGA) renin increased and ACE2 decreased in CK cortex, leading to elevate ACE/ACE2 ratio. At 5w, up-regulated ACE and down-regulated ACE2 with enhanced renin in collecting duct were found in both kidneys medulla, especially in NCK. Also AT1R in CK cortex was not suppressed albeit reduced MasR, therefore, AT1R/MasR ratio was elevated. Conclusions: Intrarenal RAS was changed depending on the time, part and sides of 2K1C rat kidneys. The attenuated ACE2 with augmented JGA renin in CK contributed to initiate hypertension and aggravated imbalanced ACE relative to ACE2 with activated renin in collecting duct have a key role to maintain hypertension.

Abstract P165: Exploration of the Mechanism in Which Saccharina Japonica Alleviates an Increase in Blood Pressure in Renovasucular Hypertensive Rats

Objective: Saccharina japonica (SJ), one of brown algae, is a common foodstuff in Japan and neighbor countries. Some studies have shown that the intake of SJ decreases blood pressure (BP) in spontaneously hypertensive rats. As well, we previously observed it in 2-kidney, 1-clip renovascular hypertensive (2K1C) rats. However, the mechanism is still unclear. One of possible components of SJ which play an important role in decreasing BP is alginate. Since alginate is richer in the roots than in the blades in SJ, in the present study, we compared the effects in alleviating BP of intake of SJ roots with that of SJ blades in 2K1C rats. We also evaluated angiotensin II receptor type 1 (AT1R) mRNA to investigate the role of renin-angiotensin system in the mechanism. Methods: Male Sprague-Dawley rats (6 wks) were treated with sham operation (SHAM) or clipping the left renal artery (2K1C). After surgery, the rats started receiving a control diet (C) or a diet containing 5.0% (w/w) SJ blades (B), or SJ roots (R) for 6 weeks. The systolic BP (SBP) was measured by a tail-cuff method every week. At the end of the protocol, mean arterial pressure (MAP) was measured in each rat under anesthesia. Then, the aortas were removed for extracting mRNA. AT1R-mRNA expression was evaluated using reverse transcriptase quantitative real-time PCR. Results: SBP was significantly higher in 2K1C-C than SHAM-C through the experiment period (p&lt;0.001). SBP in 2K1C-B and -R was significantly lower than in 2K1C-C (p&lt;0.001). 2K1C-B showed a significant reduction in SBP compared with in 2K1C-R (p&lt;0.05). At the end of the protocol, MAP showed the similar trend to SBP. AT1R mRNA expression was higher in 2K1C than in SHAM, but there were no significant differences among 2K1C-C, -B and -R. Conclusion: Although alginate is richer in the roots than in the blades in SJ, the effects in alleviating BP was higher in the blades than in the roots. Thus, alginate may play no major role in the mechanism. AT1R may not play an important role, neither. Therefore, we need investigate other possible mechanisms.

PP.LB02.15] RENAL DENERVATION NORMALIZES SYMPATHETIC VASOMOTOR ACTIVITY AND PRODUCES DIFFERENTIAL EFFECTS ON THE ARTERIAL BARORECEPTOR FUNCTION IN THE GOLDBLATT RENOVASCULAR HYPERTENSION

Objective: Sympathetic nerve activity is increased in renovascular hypertension. Renal denervation has shown promise in the treatment of patients with resistant hypertension to drug therapy, although the mechanisms underlying reduction in blood pressure remains uncertain. The aim of this study was to evaluate the effects of unilateral renal denervation (H+DnX) on efferent post-ganglionic sympathetic nerve activity to renal (rSNA) and lumbar (lSNA) sympathetic nerves in Goldblatt hypertensive rats (2K1C). Design and method: The baroreceptor sensitivity to rSNA, lSNA, heart rate (HR) and the cardiovascular autonomic function (by power spectral density analysis) were evaluated ten days after renal denervation. Denervation of clipped kidney (DnX – all visible bundles nerves were dissected – 10% phenol) was performed 5 weeks after clipping (gap width 0.2 mm). The rSNA and barorreceptor reflex control to rSNA was performed in the innervated contralateral kidney. Results: Ten days after DnX, blood pressure (BP) was significantly reduced (16%) in the 2K1C rats compared to 2K1C undenervated (H). DnX normalized rSNA (CT: 110 ± 8, n = 14; 2K1C:150 ± 8, n = 12; 2K1C DnX:89 ± 7, pps n = 8) and lSNA (CT: 137 ± 8, n = 8; 2K1C: 202 ± 7, n = 11; 2K1C DnX:131 ± 7, pps n = 8) in the 2K1C rats. DnX significantly improved the baroreceptor function for rSNA (CT: −2.3 ± 0.2, n = 11; 2K1C: −0.7 ± 0.1, n = 8; 2K1C DnX: −1.5 ± 0.2, pps/mmHg n = 5) and tachycardic response (CT: −3.9 ± 0.5, n = 7; 2K1C: −1.9 ± 0.1, n = 8; 2K1C DnX: −3.3 ± 0.4, bpm/mmHg n = 8), but not for lSNA in 2K1C rats. Furthermore, DnX significantly increased the high frequency (HF) component (CT: 1.4 ± 1, n = 10; 2K1C: 3.4 ± 2 n = 9; 2K1C DnX: 7.6 ± 3, ms2 n = 9) but not the very low frequency (VLF) and low frequency (LF) components (VLF = CT: 2.7 ± 1, n = 10; 2K1C: 13 ± 7, n = 9; 2K1C DnX: 9 ± 5, ms2 n = 8 / LF = CT: 2 ± 0.6, n = 9; 2K1C: 5 ± 3, n = 11; 2K1C DnX: 6 ± 4, ms2 n = 9) which remained elevated in the 2K1C rats. Conclusions: The results show that renal denervation normalized sympathetic vasomotor activity and increased the HF component of spectral analysis accompanied by a non uniform improvement in the arterial baroreceptor function. Whether the baroreceptor function sensitivity improvement induced by DnX is a cause or a consequence of BP reduction remains to be determined. Supported by FAPESP and CAPES.

Matrix metalloproteinase (MMP)-2 decreases calponin-1 levels and contributes to arterial remodeling in early hypertension

Increased matrix metalloproteinase (MMP)-2 is implicated in the vascular remodeling of hypertension. Calponin-1 is a contractile protein, and its absence is associated with vascular smooth muscle cell (VSMC) phenotype switch, which leads to migration and remodeling. We evaluated whether increased MMP-2 activity precedes chronic vascular remodeling by decreasing calponin-1 and inducing VSMC proliferation. Sham or two kidney-one clip (2K1C) rats were treated with doxycycline at 30mg/kg/day. Systolic blood pressure was increased in the 2K1C rats after 1 and 2weeks post-surgery, and doxycycline was effective to reduce it only at 2weeks of hypertension (p<0.05). Increased activity of MMP-2 was observed in aortas from 2K1C at 1 and 2weeks of hypertension, followed by increased VSMC proliferation, and those effects were abolished by treating 2K1C rats with doxycycline (p<0.05). Increased aortic media to lumen ratio started to emerge in 2K1C rats at 1week of hypertension, and it was established by 2weeks. MMP-2 and calponin-1 co-localized in the cytosol of VSMC. Aortas from 2K1C rats showed a significant reduction in calponin-1 levels at 1week of hypertension, and doxycycline prevented its loss (p<0.05). However, at 2weeks of hypertension, calponin-1 was upregulated in 2K1C (p<0.05 vs. Sham groups). The mRNA levels of calponin-1 were not altered in the aortas of 2K1C at 1week of hypertension. MMP-2 may contribute to the post-translational decrease in calponin-1, thus culminating in hypertension-induced maladaptive arterial remodeling.

Oxidative stress increases the risk of pancreatic β cell damage in chronic renal hypertensive rats.

Hypertension often occurs in conjunction with insulin resistance. The purpose of this study was to evaluate whether sustained renal hypertension increases the risk of diabetes mellitus in rats, and to define the underlying mechanisms. Two‐kidney, one‐clip hypertensive (2K1C) rats received captopril (50 mg/kg/day), α‐lipoic acid (100 mg/kg/day), or vehicle treatment for 3 months after surgery. Blood pressure was measured by tail cuff plethysmography. Oral glucose tolerance test (OGTT), immunohistochemistry, and western blotting were performed. In addition, insulin secretion from islet cells was measured. OGTT yielded abnormal results, and the number of islet cells and the size of pancreatic β/α cells were decreased in 2K1C rats. Basal insulin levels were also reduced in the plasma. Insulin secretion from pancreatic islet cells in response to high glucose was also attenuated in 2K1C rats compared with sham rats. The levels of oxidative stress markers, including 8‐hydroxydeoxyguanosine and NADPH oxidase‐4, were increased in pancreatic tissue and pancreatic islets in 2K1C rats. The abnormalities observed in 2K1C rats were improved by captopril or α‐lipoic acid treatment. These findings indicate that sustained renal hypertension may lead to pancreatic dysfunction, increasing oxidative stress in pancreatic islets.