Effects of levosimendan on cardiac remodeling and cardiomyocyte apoptosis in hypertensive Dahl/Rapp rats.

BACKGROUND AND PURPOSE: Progression of heart failure in hypertensive Dahl rats is associated with cardiac remodeling and increased cardiomyocyte apoptosis. This study was conducted to study whether treatment with a novel inotropic vasodilator compound, levosimendan, could prevent hypertension-induced cardiac remodeling and cardiomyocyte apoptosis. EXPERIMENTAL APPROACH: 6-week-old salt-sensitive Dahl/Rapp rats received levosimendan (0.3 mg kg(-1) and 3 mg kg(-1) via drinking fluid) and high salt diet (NaCl 7%) for 7 weeks, Dahl/Rapp rats on low-salt diet served as controls. Blood pressure, cardiac functions by echocardiography, cardiomyocyte apoptosis by TUNEL technique, tissue morphology, myocardial expression of calcium cycling proteins, and markers of neurohumoral activation were determined. KEY RESULTS: Untreated Dahl/Rapp rats on high salt diet developed severe hypertension, cardiac hypertrophy and moderate systolic dysfunction. 38% of Dahl/Rapp rats (9/24) survived the 7-week-follow-up period. Cardiomyocyte apoptosis was increased by 6-fold during high salt diet. Levosimendan improved survival (survival rates in low- and high-dose levosimendan groups 12/12 and 9/12, p<0.001 and p=0.05, respectively), increased cardiac function, and ameliorated cardiac hypertrophy. Levosimendan dose-dependently prevented cardiomyocyte apoptosis. Levosimendan normalized salt-induced increased expression of natriuretic peptide, and decreased urinary noradrenaline excretion. Levosimendan also corrected salt-induced decreases in myocardial SERCA2a protein expression and myocardial SERCA2a/NCX-ratio. CONCLUSIONS AND IMPLICATIONS: Improved survival by the novel inotropic vasodilator levosimendan in hypertensive Dahl/Rapp rats is mediated, at least in part, by amelioration of hypertension-induced cardiac remodeling and cardiomyocyte apoptosis.

Lupin protein attenuates the development of hypertension and normalises the vascular function of NaCl-loaded Goto-Kakizaki rats.

The beneficial cardiovascular effects of soy protein have been studied intensively in recent years. Another protein-rich legume is lupin, which has been shown to have similar effects to those of soy in lowering serum cholesterol levels. In this study we compared the effects of lupin and soy protein on hypertension and vascular functions in spontaneously diabetic Goto-Kakizaki (GK) rat, which develop hypertension when fed a high-salt diet. The rats were fed with a 6% NaCl diet containing either lupin or soy protein isolate (20% weight/weight) for two weeks. In the end of the study the SBP was 18.6 mmHg lower (p<0.001) in the lupin group, and 12.0 mmHg lower (p<0.01) in the soy group than in the control group. Lupin and soy treatments normalised the decreased vasocontraction observed in the NaCl-fed control group, but only lupin treatment improved the impaired endothelium-dependent vasorelaxation. The attenuation of hypertension is likely to be mediated by the corrected vascular dysfunction, whose precise mechanism and the possible clinical relevance remains to be studied further.

Beneficial effects of a potassium- and magnesium-enriched salt alternative.

The effects on blood pressure and the development of cardiac hypertrophy of sodium chloride (regular salt) and a novel potassium-, magnesium-, and l-lysine-enriched salt alternative, which in a previous study prolonged the life span of hypertensive rats nearly threefold as compared with the animals receiving regular salt, were compared both in spontaneously hypertensive rats and their hypertension-resistant genetic controls. In particular, the possible protective effect of increased intakes of potassium, magnesium, and l-lysine during a high intake of sodium chloride was examined. Therefore, the salt alternative was added at 1.75 times higher levels to produce the same dietary levels of sodium chloride in the regular salt and the salt alternative groups. Regular salt produced a remarkable left ventricular hypertrophy in both rat strains, but as compared with the respective control groups, it induced an increase of blood pressure only in the spontaneously hypertensive rats. The salt alternative did not induce a rise in blood pressure in either of the rat strains, nor did it produce left ventricular hypertrophy in the hypertension-resistant rats and, in the spontaneously hypertensive animals, significantly less hypertrophy than regular salt. The salt alternative appeared to prevent the sodium chloride-induced volume load since plasma levels of atrial natriuretic peptide were increased in the regular salt groups but remained normal in the salt alternative groups. Therefore, potassium, magnesium, and/or l-lysine of the salt alternative produced a powerful protection against the harmful effects of sodium chloride.

NF-kappaB inhibition ameliorates angiotensin II-induced inflammatory damage in rats.

We recently reported that the activation of nuclear factor-kappaB (NF-kappaB) promotes inflammation in rats harboring both human renin and angiotensinogen genes (double-transgenic rats [dTGR]). We tested the hypothesis that the antioxidant pyrrolidine dithiocarbamate (PDTC) inhibits NF-kappaB and ameliorates renal and cardiac end-organ damage. dTGR feature hypertension, severe renal and cardiac damage, and a 40% mortality rate at 7 weeks. Electrophoretic mobility shift assay showed increased NF-kappaB DNA binding activity in hearts and kidneys of dTGR. Chronic PDTC (200 mg/kg SC) treatment decreased blood pressure (162+/-8 versus 190+/-7 mm Hg; P=0.02) in dTGR compared with dTGR controls. The cardiac hypertrophy index was also significantly reduced (4.90+/-0.1 versus 5.77+/-0.1 mg/g; P<0. 001). PDTC reduced 24-hour albuminuria by >95% (2.5+/-0.8 versus 57. 1+/-8.7 mg/d; P<0.001) and prevented death. Vascular injury was ameliorated in small renal and cardiac vessels. Electrophoretic mobility shift assay showed that PDTC inhibited NF-kappaB binding activity in heart and kidney, whereas AP-1 activity in the kidney was not decreased. dTGR exhibited increased left ventricular c-fos and c-jun mRNA expression. PDTC treatment reduced c-fos but not c-jun mRNA. Immunohistochemistry showed increased p65 NF-kappaB subunit expression in the endothelium and smooth muscle cells of damaged small vessels, as well as infiltrating cells in glomeruli, tubules, and collecting ducts of dTGR. PDTC markedly reduced the immunoreactivity of p65. PDTC also prevented the NF-kappaB-dependent transactivation of the intercellular adhesion molecule ICAM-1 and inducible nitric oxide synthase. Monocyte infiltration was markedly increased in dTGR kidneys and hearts. Chronic treatment reduced monocyte/macrophage infiltration by 72% and 64%, respectively. Thus, these results demonstrate that PDTC inhibits NF-kappaB activity, ameliorates inflammation, and protects against angiotensin II-induced end-organ damage.

Effects of dietary sodium and magnesium on cyclosporin A-induced hypertension and nephrotoxicity in spontaneously hypertensive rats.

Arterial hypertension, nephrotoxicity, and magnesium loss are common side effects of the immunosuppressive agent cyclosporin A (CsA). In the present study, the effects of dietary sodium and magnesium on CsA toxicity were examined in spontaneously hypertensive rats. A 6-week treatment with CsA during a moderately low-sodium diet (Na 0.3%, Mg 0.2% of the dry weight of the chow) raised blood pressure only slightly, without evidence of nephrotoxicity. By contrast, CsA during a high-sodium diet (Na 2.6%) produced a pronounced rise in blood pressure as well as marked nephrotoxicity, comprising decreased creatinine clearance, increased levels of serum creatinine and urea, and increased urinary protein excretion. During the high-sodium diet, CsA decreased myocardial and bone magnesium concentration and increased myocardial and renal calcium concentration. Magnesium supplementation (Mg 0.6%) protected against the CsA-induced hypertension and nephrotoxicity during the high-sodium diet. Magnesium supplementation also completely prevented the CsA-induced myocardial magnesium depletion and calcium accumulation in the heart and kidney during the high-sodium diet. Our findings indicate a detrimental interaction between increased sodium intake and CsA treatment and a marked protection by concomitant oral magnesium supplementation.

Monocyte infiltration and adhesion molecules in a rat model of high human renin hypertension.

Hypertension and kidney damage in the double transgenic rat (dTGR) harboring both human renin and human angiotensinogen genes are dependent on the human components of the renin angiotensin system. We tested the hypothesis that monocyte infiltration and increased adhesion molecule expression are involved in the pathogenesis of kidney damage in dTGR. We also evaluated the effects of long-term angiotensin-converting enzyme (ACE) inhibition, AT1 blockade, and human renin inhibition on monocyte recruitment and inflammatory response in dTGR. Systolic blood pressure and 24-hour albuminuria were markedly increased in 7-week-old dTGR as compared with age-matched normotensive Sprague Dawley rats. We found a significant monocyte/macrophage infiltration in the renal perivascular space and increased expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the interstitium, intima, and adventitia of the small renal vessels. alphaLbeta2 integrin and alpha4beta1 integrin, the corresponding ligands for ICAM-1 and VCAM-1, were also found on infiltrating monocytes/macrophages. The expression of plasminogen activator inhibitor-1 and fibronectin in the kidneys of dTGR were increased and distributed similarly to ICAM-1. In 4-week-old dTGR, long-term treatment with ACE inhibition (cilazapril), AT1 receptor blockade (valsartan), and human renin inhibition (RO 65-7219) (each drug 10 mg/kg by gavage once a day for 3 weeks) completely prevented the development of albuminuria. However, only cilazapril and valsartan were able to decrease blood pressure to normotensive levels. Interestingly, the drugs were all equally effective in preventing monocyte/macrophage infiltration and the overexpression of adhesion molecules, plasminogen activator inhibitor-1, and fibronectin in the kidney. Our findings indicate that angiotensin II causes monocyte recruitment and vascular inflammatory response in the kidney by blood pressure-dependent and blood pressure-independent mechanisms. ACE inhibition, AT1 receptor blockade, and human renin inhibition all prevent monocyte/macrophage infiltration and increased adhesion molecule expression in the kidneys of dTGR.

Effect of bosentan on NF-kappaB, inflammation, and tissue factor in angiotensin II-induced end-organ damage.

Reports on the effectiveness of endothelin receptor blockers in angiotensin (Ang) II-induced end-organ damage are conflicting, and the mechanisms involved are uncertain. We tested the hypothesis that endothelin (ET)(A/B) receptor blockade with bosentan (100 mg/kg by gavage after age 4 weeks) ameliorates cardiac and renal damage by decreasing inflammation in rats harboring both human renin and angiotensinogen genes (dTGR). Furthermore, we elucidated the effect of bosentan on tissue factor (TF), which is a key regulator of the extrinsic coagulation cascade. We compared bosentan with hydralazine (80 mg/L in the drinking water for 3 weeks) as a blood pressure control. Untreated dTGR featured hypertension, focal necrosis in heart and kidney, and a 45% mortality rate (9 of 20) at age 7 weeks. Compared with Sprague-Dawley controls, both systolic blood pressure and 24-hour albuminuria were increased in untreated dTGR (203+/-8 versus 111+/-2 mm Hg and 67.1+/-8.6 versus 0.3+/-0.06 mg/d at week 7, respectively). Bosentan and hydralazine both reduced blood pressure and cardiac hypertrophy. Mortality rate was markedly reduced by bosentan (1/15) and partially by hydralazine (4/15). However, only bosentan decreased albuminuria and renal injury. Untreated and hydralazine-treated dTGR showed increased nuclear factor (NF)-kappaB and AP-1 expression in the kidney and heart; the p65 NF-kappaB subunit was increased in the endothelium, vascular smooth muscles cells, infiltrating cells, glomeruli, and tubules. In the heart and kidney, ET(A/B) receptor blockade inhibited NF-kappaB and AP-1 activation compared with hydralazine treatment. Macrophage infiltration, ICAM-1 expression, and the integrin expression on infiltrating cells were markedly reduced. Renal vasculopathy was accompanied by increased tissue factor expression on macrophages and vessels of untreated and hydralazine-treated dTGR, which was markedly reduced by bosentan. Thus, ET(A/B) receptor blockade inhibits NF-kappaB and AP-1 activation and the NF-kappaB- and/or AP-1-regulated genes ICAM-1, VCAM-1, and TF, independent of blood pressure-related effects. We conclude that Ang II-induced NF-kappaB and AP-1 activation and subsequent inflammation and coagulation involve at least in part the ET(A/B) receptors.

Improvement of cardiovascular effects of metoprolol by replacement of common salt with a potassium- and magnesium-enriched salt alternative.

1. The influence of sodium chloride (NaCl)-enrichment of the diet (6% of the dry weight) and that of a novel sodium-reduced, potassium-, magnesium-, and L-lysine-enriched salt alternative on the cardiovascular effects of the beta 1-adrenoceptor blocking drug, metoprolol, was studied in stroke-prone spontaneously hypertensive rats. 2. Increased dietary sodium chloride intake produced a marked rise in blood pressure and induced left ventricular and renal hypertrophy. By contrast, the salt alternative did not increase blood pressure and caused remarkably less cardiac and renal hypertrophy than did sodium chloride. 3. Metoprolol treatment at a daily dose of 250 mg kg-1 lowered blood pressure and decreased left ventricular hypertrophy index during the control diet. Sodium chloride-enrichment blocked the antihypertensive effect of metoprolol, while a partial protective effect on left ventricular and renal hypertrophy persisted. In the presence of the salt alternative-enrichment both at the level of 6% and 10.5% (corresponding to a NaCl level of 6%), metoprolol was fully able to exert its beneficial cardiovascular and renal effects. 4. Both salt supplementations, irrespective of metoprolol treatment, induced a 3 to 4 fold increase in the urinary excretion of calcium. There was a linear correlation between the urinary excretions of sodium and calcium. The urinary excretion of magnesium rose by 90% and that of potassium by 110% in the salt alternative group. 6. Our findings suggest that replacement of common salt by a potassium-, and magnesium-enriched salt alternative in the diet produces beneficial cardiovascular effects and improves the antihypertensive efficacy of metoprolol in stroke-prone spontaneously hypertensive rats. Increased intake of potassium and/or magnesium and L-lysine from the salt alternative is involved in the beneficial effects of the salt alternative. The NaCl-induced myocardial and renal hypertrophies appear to be partially mediated by Beta-adrenoceptor activation.

Cardiovascular effects of a low-dose combination of ramipril and felodipine in spontaneously hypertensive rats.

1. Cardiovascular effects of submaximal antihypertensive doses of the angiotensin converting enzyme inhibitor, ramipril (0.25 mg kg-1 day-1 in the food), and the calcium channel blocker, felodipine (0.4 mg kg-1 day-1 subcutaneously by osmotic minipump), both alone and in combination, were examined in spontaneously hypertensive rats (SHR) in a four-week study. 2. Both ramipril and felodipine as monotherapy decreased systolic blood pressure. The antihypertensive effect of the drug combination was more than that of ramipril treatment alone, but not significantly better than that of felodipine monotherapy. Ramipril or felodipine treatments did not significantly affect the heart rate, either alone or in combination. 3. The beneficial effect of ramipril monotherapy on left ventricular hypertrophy was more prominent than that of felodipine. The cardioprotective effect of felodipine was improved when combined to ramipril. The systolic blood pressure at the end of the experimental period correlated only weakly with left ventricular hypertrophy. 4. Responses of mesenteric arterial rings in vitro were examined at the end of the four-week study. Ramipril and felodipine monotherapies as well as their combination markedly improved the endothelium-dependent vascular relaxation responses to acetylcholine. The combination of ramipril and felodipine slightly enhanced the endothelium-independent vascular relaxation responses to sodium nitroprusside. Ramipril treatment alone slightly diminished the vascular contractile responses to noradrenaline. Neither ramipril nor felodipine alone or in combination affected the vascular contractile responses to potassium chloride. 5. Ramipril treatment, both alone and in combination with felodipine, caused a three fold increase in plasma renin activity. Serum aldosterone, fasting blood glucose level, serum insulin and the 24 hour urinary excretions of sodium, potassium, magnesium, calcium, phosphorus or protein were not significantly affected by the drug treatments. 6. Our findings suggest that a better overall control of hypertension and end-organ damages, without an increase in adverse effects, can be achieved by the combination of submaximal antihypertensive doses of felodipine and ramipril than by monotherapy with either drug alone.

Influence of dietary salts on the cardiovascular effects of low-dose combination of ramipril and felodipine in spontaneously hypertensive rats.

1 In spontaneously hypertensive rat (SHR) we examined over a 4-week period the influence of control low sodium diet, common salt-enriched diet (sodium chloride 6% of the dry weight of the chow) and a novel mineral salt-enriched diet (potassium-, magnesium-, and l-lysine-enriched mineral salt added at a 75% higher level of 10.5% to produce the same sodium chloride concentration of 6%) on the cardiovascular effects produced by a low-dose combination of an angiotensin converting enzyme inhibitor ramipril (0.25 mg kg(-1) day(-1) in the food) and a calcium channel blocker felodipine (0.4 mg kg(-1) day(-1) subcutaneously via an osmotic minipump). 2 Common salt, but not the mineral salt, accelerated the development of hypertension and induced left ventricular and renal hypertrophy in SHR. Neither common salt nor mineral salt significantly affected heart rate. 3 The combination of ramipril and felodipine decreased systolic blood pressure and prevented the development of left ventricular hypertrophy effectively during the common salt diet without any significant effect on the heart rate. The cardiovascular effects of the drug combination were improved by the low sodium diet or by replacement of high common salt in the diet by mineral salt. 4 Responses of endothelium-intact mesenteric arterial rings in vitro were examined at the end of the four-week study. The combination of ramipril and felodipine markedly improved the endothelium-dependent vascular relaxation responses to acetylcholine and enhanced the endothelium-independent vascular relaxation responses to sodium nitroprusside in SHR on control and common salt diets. Replacement of common salt in the diet by mineral salt improved the endothelium-dependent vascular relaxation responses to acetylcholine. The drug combination attenuated the alpha-adrenoceptor-mediated vascular contractile responses to noradrenaline during the common salt diet. 5 Ramipril and felodipine in combination increased plasma renin activity by 1.9-3.2 fold without affecting serum aldosterone levels. 6 Our findings suggest that the cardiovascular effect of the low-dose combination of ramipril and felodipine was maintained during high salt intake. However, salt restriction or replacement of common salt in the diet by the potassium- and magnesium-enriched mineral salt improved the cardiovascular effects of the drug combination. In the face of a high intake of sodium, a part of the beneficial cardiovascular effects of the drug combination is apparently mediated by improved endothelium-dependent and endothelium-independent vascular relaxation responses and attenuated alpha-adrenoceptor-mediated vascular contractile responses.

Replacement of salt by a novel potassium- and magnesium-enriched salt alternative improves the cardiovascular effects of ramipril.

1. The influence of salt (sodium chloride; NaCl) (an additional 6% in the diet) and that of a novel sodium-reduced, potassium-, magnesium-, and L-lysine-enriched salt alternative on the cardiovascular effects of ramipril was studied in stroke-prone spontaneously hypertensive rats in a 6-week study. The intake of sodium chloride was adjusted to the same level by adding the salt alternative at a 1.75 times higher amount than regular salt. 2. Salt produced a marked rise in blood pressure and induced cardiac hypertrophy and significant mortality, while the salt alternative neither increased blood pressure nor caused any mortality and produced less cardiac hypertrophy than salt. 3. Ramipril treatment at a daily dose of 3 mg kg-1 normalized blood pressure and prevented the development of cardiac hypertrophy of rats on control diet. These effects of ramipril were blocked by the addition of salt but were only slightly attenuated by the addition of the salt alternative. The mortality in the salt group was prevented by ramipril. 4. Responses of mesenteric arterial rings in vitro were examined at the end of the study. Salt, but not the salt alternative, increased vascular contractile responses to noradrenaline. Ramipril treatment improved the arterial relaxation responses to acetylcholine and to sodium nitroprusside. The vascular relaxation enhancing effect of ramipril was blocked by salt but only slightly attenuated by the salt alternative. 5. Ramipril treatment did not significantly increase plasma renin activity in the presence or in the absence of salt supplementation. The salt alternative did not cause hyperkalaemia, either alone or in combination with ramipril treatment. 6. Both salt supplementations, irrespective of ramipril treatment, induced a six to eight fold increase in the urinary excretion of calcium. There was an expected 90 to 140% rise in the urinary excretion of magnesium and 200% rise in the urinary excretion of potassium in the salt alternative group. Salt also produced an approximately 50% increase in magnesuria.7. Our findings suggest that replacement of salt by the potassium-, magnesium- and L-lysine-enriched salt alternative improves the cardiovascular effects of ramipril. In the present study the beneficial effect was related to the increased intakes of potassium and/or magnesium and L-lysine from the salt alternative because the amount of sodium chloride was the same.

Beneficial effects of dietary magnesium and potassium on cardiac and renal morphologic features in cyclosporin A-induced damage in spontaneously hypertensive rats.

BACKGROUND: Cyclosporin A-induced hypertension is dependent on the level of dietary salt. We investigated whether dietary magnesium or potassium could protect against cyclosporin A-induced cardiac and renal damage in spontaneously hypertensive rats (SHRs) on high-sodium diet. METHODS: Eight-week-old SHRs were divided into 4 groups: (1) receiving a high-sodium diet, (2) receiving a high-sodium, high-potassium diet, (3) receiving a high-sodium, high-magnesium diet, and (4) receiving a high-sodium, high-potassium, high-magnesium diet. The effects of cyclosporin A in SHRs on a relatively low-sodium diet and in normotensive Wistar-Kyoto rats were also examined. Cardiac and renal morphologic condition was assessed, and tissue damage was scored by light microscopy after 6 weeks of cyclosporin A treatment. RESULTS: In SHRs on a high-sodium diet, cyclosporin A caused luminal narrowing of the coronary arteries, left ventricular scarring, and damage in the renal arterioli and glomeruli. Dietary magnesium supplementation alone and in combination with potassium protected against these changes, whereas potassium alone was less effective. Cyclosporin A treatment caused only minor histopathologic changes in SHRs receiving a low-sodium diet. Interestingly, the detrimental interaction between cyclosporin A and a high-sodium diet was also observed in normotensive Wistar-Kyoto rats. CONCLUSIONS: Dietary magnesium, especially in combination with potassium, protects against cyclosporin A-induced cardiac and renal damage.

Cardiovascular effects of felodipine are not antagonized by dietary salt.

Increased dietary intake of regular salt (sodium chloride) interferes markedly with the therapeutic effects of angiotensin converting enzyme inhibitors. To study further the interactions between dietary salt intake and antihypertensive drug treatment, we examined the effects of felodipine, a dihydropyridine derivative Ca2+ channel antagonist with natriuretic properties, on blood pressure and the development of left ventricular hypertrophy in the stroke-prone spontaneously hypertensive rats during different levels of sodium chloride in the diet. We also compared the influence of regular salt on the cardiovascular effects of felodipine with that of a novel K(+)-, Mg(2+)- and l-lysine-enriched and Na(+)-reduced salt alternative, which in previous studies markedly improved the therapeutic effects of enalapril and ramipril. During the 28-day experiment regular salt produced a marked rise in blood pressure and induced left ventricular hypertrophy, while the salt alternative neither induced any rise of blood pressure nor caused cardiac hypertrophy. Felodipine had an enhanced antihypertensive effect during the increased intake of sodium chloride, and lowered the blood pressure to the same normotensive level as it did during the control and the salt alternative diets. Felodipine also completely blocked the development of the sodium chloride-induced cardiac hypertrophy. The heart rate of the felodipine-treated animals was significantly increased during the first two study weeks but thereafter it did not differ from that of the controls. Hence, unlike regular salt, the novel Na(+)-reduced, K(+)-, Mg(2+)-, and l-lysine-enriched salt alternative did not raise blood pressure and produced little if any left ventricular hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of enalapril and hydrochlorothiazide on the salt-induced cardiac and renal hypertrophy in normotensive rats.

Recent studies have shown that, not only in hypertensive animals but even in normotensive rats, dietary salt (sodium chloride) produces a dose-related increase in the left ventricular and renal mass. In the present study the effects of the angiotensin converting enzyme inhibitor (ACEI) enalapril and the thiazide-type diuretic, hydrochlorothiazide, on the development of the salt-induced left ventricular and kidney hypertrophy were examined in normotensive Wistar-Kyoto and Wistar rats. A high intake of sodium chloride (6% of the dry weight of the chow to mimic the level found in many human food items) during eight weeks produced a marked increase in the mass of the left ventricle and the kidneys in both rat strains with little or no effect on blood pressure. The cardiac hypertrophy correlated strongly with the renal hypertrophy. These salt-induced changes in the heart and in the kidneys were completely blocked by hydrochlorothiazide, while enalapril was devoid of any significant effects during the high-salt diet. However, during a low-salt diet enalapril, but not hydrochlorothiazide, effectively lowered the blood pressure and decreased the left ventricular mass of the normotensive rats. There was a 3- to 4-fold increase in the urinary excretion of calcium during the high intake of sodium chloride. Hydrochlorothiazide decreased the urinary excretion of calcium even during the low salt diet, and it completely blocked the salt-induced hypercalciuria. Enalapril had no significant effect on the urinary calcium excretion. During the low-salt diet hydrochlorothiazide increased the calcium and decreased the potassium concentration in the heart while enalapril increased the phosphorus concentration. In conclusion, a high intake of sodium chloride produced hypertrophy both in the heart and in the kidneys, even in the absence of a rise in blood pressure. Salt also remarkably increased the urinary calcium excretion. These harmful effects of salt were blocked by the thiazide diuretic hydrochlorothiazide but not by the ACEI enalapril. However, this study does not allow to make any direct comparison between the effects of enalapril and hydrochlorothiazide.

Influence of different dietary salts on the cardiovascular and renal effects of moxonidine in spontaneously hypertensive rats.

The influence of common salt (NaCl) and a novel potassium-, magnesium-, and L-lysine-enriched mineral salt on the cardiovascular and renal effects of the selective imidazoline I1-receptor agonist moxonidine was examined in spontaneously hypertensive rats (SHR). Common salt was added at the level of 6% of the dry weight of the chow, and mineral salt at a 75% higher level of 10.5% thereof to produce the same NaCl concentration of 6% as in the common salt group. During the control diet an 8-week oral treatment with moxonidine (117 mg/1000 g of the dry weight of the chow producing an approximate daily dose of 10 mg/kg), lowered blood pressure by 13 mmHg. The common salt diet alone raised blood pressure by 27 mmHg. Moxonidine lowered blood pressure by 21 mmHg during the common salt diet, but the blood pressure remained 19 mmHg higher than in the moxonidine-treated SHR receiving the control diet (P<0.05). Unlike common salt, mineral salt alone did not raise blood pressure nor did it interfere with the antihypertensive effect of moxonidine. Moxonidine showed a kidney-protective effect during the control diet measured as decreased urinary protein excretion, but it did not affect the development of left ventricular hypertrophy. Moxonidine increased plasma renin activity during the control diet and it raised the serum aldosterone level both during the control and mineral salt diets. The vascular relaxation responses of the mesenteric arterial rings to both acetylcholine (an indicator of endothelium-dependent vascular relaxation) and nitroprusside and nitroprusside (an indicator of endothelium-independent vascular relaxation) were attenuated by the common salt diet alone but maintained during the moxonidine treatment. Our findings are consistent with the concept that moxonidine is able to improve the excretion of sodium. This effect might explain the maintenance of normal vascular relaxation during a high intake of common salt. These effects may partly account for the antihypertensive effect of moxonidine.

Vascular effects of COX inhibition and AT1 receptor blockade in transgenic rats harboring mouse renin-2 gene.

Ang II-induced endothelial dysfunction is associated with perivascular inflammation and increased superoxide production in the vascular wall. The present study examined the role of cyclo-oxygenase (COX)-synthetized eicosanoids in the pathogenesis of Ang II-induced endothelial dysfunction in transgenic rats harboring mouse renin-2 gene (mREN2 rats). Five-to-six-week-old, heterozygous mREN2 rats received the following drug regimens for 8 weeks: 1) vehicle, 2) cyclo-oxygenase-2 (COX-2) inhibitor (MF-tricyclic [3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl) phenyl)-2(5H)-furanone], 14 mg/kg p.o.), 3) COX-1/COX-2 inhibitor (sulindac, 14 mg/kg p.o.), 4) angiotensin II receptor antagonist (losartan 40 mg/kg p.o.). Normotensive Sprague Dawley (SD) rats served as controls. In vitro vascular responses of the descending aorta and renal artery were studied using organ bath system. mREN2 rats developed pronounced hypertension which was associated with impaired endothelium-dependent and endothelium-independent vascular relaxations in the aorta. In contrast, the relaxation responses of the renal arteries remained largely unchanged in mREN2 rats. Urinary NO, excretion, a marker of total body NO generation, was also decreased in mREN2 rats. Neither non-selective COX inhibitor sulindac nor COX-2 selective MF-tricyclic were capable of preventing Ang II-induced hypertension or endothelial dysfunction in mREN2 rats, whereas ATi receptor antagonist losartan completely normalized blood pressure, vascular relaxation responses as well as urinary NOx excretion. Our findings indicate that NO synthesis and/or bioavailability as well as the sensitivity of arterial smooth muscle cells to NO are decreased in mREN2 rats. The present study also demonstrated that COX does not play a central role in the pathogenesis of Ang II-induced endothelial dysfunction in mREN2 rats.

Influence of age on cardiovascular effects of increased dietary sodium and angiotensin-converting enzyme inhibition in normotensive Wistar rats.

Recent studies have shown that increased intake of dietary sodium chloride produces blood pressure-independent increase in cardiac and renal mass even in young normotensive rats. With advancing age the harmful cardiovascular effects of increased dietary sodium are not so well known. In the present study the influence of advancing age on the cardiovascular effects of increased intake of sodium (control diet, 0.3% and high-sodium diet, 2.6% sodium in the chow) were examined in young and aged (3 and 18 months old, respectively, at the beginning of the experiment) male normotensive Wistar rats in a six-week study. Moreover, the potential role of renin-angiotensin system in ageing during normal and a high-sodium intake was studied using a pharmacological tool, angiotensin converting enzyme (ACE) inhibitor ramipril. Ageing did not significantly modify basal systolic blood pressure measured by the tail cuff method. A high intake of sodium chloride increased blood pressure significantly only in aged rats, while in young rats it increased renal weight. Left ventricular weight was not affected by high-sodium diet in either age group. The ACE inhibition during control diet lowered blood pressure and decreased left ventricular weight in young rats only and these effects were completely blocked by a high-sodium diet. The maximal vascular contraction force of mesenteric arterial rings to noradrenaline was decreased with ageing while endothelium-dependent and -independent relaxation responses were unaltered with ageing. The sensitivity to sodium nitroprusside was impaired by the high-sodium diet in young rats. In both age groups the urinary excretion of calcium was increased during the high-sodium diet. In conclusion, the increased intake of sodium produced different changes in cardiovascular function in normotensive rats depending on age. With advancing age, the sensitivity to sodium-induced increase in blood pressure was increased. In aged rats a high intake of dietary sodium elevated blood pressure, while in young rats it increased renal mass without increase in blood pressure. In both age groups sodium did not affect left ventricular hypertrophy. Both high-sodium intake and ageing attenuated or even abolished the cardiovascular effects of ACF inhibition.

Influence of age and dietary sodium on the cardiovascular and renal effects of ramipril in spontaneously hypertensive rats.

The aim of the present study was to investigate the influence of age and an increased intake of dietary sodium on the cardiovascular and renal effects of the angiotensin converting enzyme inhibitor, ramipril. Male spontaneously hypertensive rats (SHR) aged 10 and 60 weeks received either control or a high level of sodium (0.3% vs. 2.6% Na) and ramipril (2 mg/kg/day) mixed in the chow for 6 weeks. Blood pressure was measured weekly by tail-cuff method. Arterial functions were determined by measuring vascular contractile and relaxation responses of mesenteric arterial rings in vitro at the end of the study. An age-related increase in systolic blood pressure, left ventricular (LVH) and renal hypertrophy (RH) as well as proteinuria were found in SHR. The vascular relaxation to nitroprusside was impaired in aged SHR. The high sodium intake accelerated the development of hypertension only in young SHR but increased LVH and RH in both age groups. Ramipril effectively lowered blood pressure in both age groups, but decreased the LVH significantly only in young rats. Ramipril markedly improved the vascular relaxation to acetylcholine and nitroprusside only in young rats. The vascular contractile responses to noradrenaline and potassium chloride were not affected by age, sodium intake or ramipril treatment. The high sodium intake markedly attenuated the cardiovascular effects of ramipril. The high-sodium diet enhanced the urinary excretion of cyclic GMP in both age groups, while it increased urinary excretion of protein in young SHR only. In conclusion, the cardiovascular effects of ramipril were impaired with advanced age even in the presence of a control intake of sodium. A high sodium intake attenuated or even abolished the cardiovascular effects of ramipril in both young and aged SHR.

Piperidine renin inhibitors: from leads to drug candidates.

Non-peptidomimetic renin inhibitors of the piperidine type represent a novel structural class of compounds potentially free of the drawbacks seen with peptidomimetic compounds so far. Synthetic optimization in two structural series focusing on improvement of potency, as well as on physicochemical properties and metabolic stability, has led to the identification of two candidate compounds 14 and 23. Both display potent and long-lasting blood pressure lowering effects in conscious sodium-depleted marmoset monkeys and double transgenic rats harboring both the human angiotensinogen and the human renin genes. In addition, 14 normalizes albuminuria and kidney tissue damage in these rats when given over a period of 4 weeks. These data suggest that treatment of chronic renal failure patients with a renin inhibitor might result in a significant improvement of the disease status.

Caloric restriction ameliorates kidney ischaemia/reperfusion injury through PGC-1α-eNOS pathway and enhanced autophagy.

AIM: We investigated whether preconditioning with caloric restriction (CR) ameliorates kidney ischaemia/reperfusion (I/R) injury and whether the salutary effects of CR are mediated through enhanced autophagy and/or activation of key metabolic sensors SIRT1, AMP-kinase and PGC-1α. METHODS: Six- to seven-week-old Wistar rats were divided into three groups: (i) sham-operated group; (ii) I/R group (40-min ischaemia followed by 24 h of reperfusion); and (iii) I/R group kept under CR (energy intake 70%) for 2 weeks before surgery. In additional experiments, sirtinol and 3-methyladenine (3-MA) were used as inhibitors of SIRT1 and autophagy respectively. Renal function was measured, and acute tubular damage and nitrotyrosine expression were scored. Kidney adenosine monophosphate-activated kinase (AMPK), SIRT1, eNOS, PGC-1α and LC-3B expressions were measured. RESULTS: Caloric restriction improved renal function, protected against the development of acute tubular necrosis and attenuated I/R-induced nitrosative stress. Kidney I/R injury decreased eNOS and PGC-1α expression, inhibit autophagy and increased SIRT1 and AMPK expressions by 2.6- and fourfold respectively. However, phosphorylation level of AMPK was decreased. As compared with I/R injury group, CR further increased kidney SIRT1 expression by 1.8-fold, promoted autophagy and counteracted I/R-induced decreases in the expression of eNOS and PGC-1α. 3-MA abolished the renoprotective effects of CR, whereas sirtinol did not influence renal function in CR rats with I/R injury. CONCLUSIONS: Caloric restriction ameliorates acute kidney I/R injury through enhanced autophagy and counteraction of I/R-induced decreases in the renal expression of eNOS and PGC-1α.