Renal responses to angiotensin receptor antagonist and angiotensin-converting enzyme inhibitor in partially nephrectomized spontaneously hypertensive rats

Dietary salt modifies the blood pressure response to renin-angiotensin inhibition in experimental chronic kidney disease

Chronic kidney disease contributes to hypertension, but the mechanisms are incompletely understood. To address this, we applied the 5/6th nephrectomy rat model to characterize hypertension and the response to dietary salt and renin-angiotensin inhibition. 5/6th nephrectomy caused low-renin, salt-sensitive hypertension with hyperkalemia and unsuppressed aldosterone. Compared with sham rats, 5/6th nephrectomized rats had lower Na⁺/H⁺ exchanger isoform 3, Na⁺-K⁺-2Cl^- cotransporter, Na⁺-Cl^- cotransporter, α-epithelial Na⁺ channel (ENaC), and Kir4.1 levels but higher serum and glucocorticoid-regulated kinase 1, prostasin, γ-ENaC, and Kir5.1 levels. These differences correlated with plasma renin, aldosterone, and/or K⁺. On a normal-salt diet, adrenalectomy (0 ± 9 mmHg) and spironolactone (-11 ± 10 mmHg) prevented a progressive rise in blood pressure (10 ± 8 mmHg), and this was enhanced in combination with losartan (-41 ± 12 and -43 ± 9 mmHg). A high-salt diet caused skin Na⁺ and water accumulation and aggravated hypertension that could only be attenuated by spironolactone (-16 ± 7 mmHg) and in which the additive effect of losartan was lost. Spironolactone also increased natriuresis, reduced skin water accumulation, and restored vasorelaxation. In summary, in the 5/6th nephrectomy rat chronic kidney disease model, salt-sensitive hypertension develops with a selective increase in γ-ENaC and despite appropriate transporter adaptations to low renin and hyperkalemia. With a normal-salt diet, hypertension in 5/6th nephrectomy depends on angiotensin II and aldosterone, whereas a high-salt diet causes more severe hypertension mediated through the mineralocorticoid receptor.NEW & NOTEWORTHY Chronic kidney disease (CKD) causes salt-sensitive hypertension, but the interactions between dietary salt and the renin-angiotensin system are incompletely understood. In rats with CKD on a normal-salt diet targeting aldosterone, the mineralocorticoid receptor (MR) and especially angiotensin II reduced blood pressure. On a high-salt diet, however, only MR blockade attenuated hypertension. These results reiterate the importance of dietary salt restriction to maintain renin-angiotensin system inhibitor efficacy and specify the MR as a target in CKD.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Pathological regression by angiotensin II type 1 receptor blockade in patients with mesangial proliferative glomerulonephritis

Although angiotensin II type 1 receptor blocker (ARB) therapy reduces proteinuria and retards the progression of renal injury in patients with glomerulonephritis, whether these drugs actually ameliorate pathological damages in human glomerulonephritis has not been determined. Fifteen patients with biopsy-proven mild-to-moderate mesangial proliferative glomerulonephritis (10 with immunoglobulin A [IgA] nephropathy and 5 with non-IgA mesangial proliferative glomerulonephritis) received ARB monotherapy. In these patients, repeated renal biopsy was performed after a mean of 28.1 months, and pathological changes (including the mesangial matrix expansion ratio and interstitial fibrosis expansion ratio) were quantitatively examined using an image analyzer. Clinical markers were also evaluated, including the serum creatinine, serum IgA, creatinine clearance (Ccr), 24-h urinary protein excretion, urinary N-acetyl-beta-D-glucosaminidase (NAG), and blood pressure. ARB therapy significantly reduced urinary protein excretion (0.68+/-0.63 to 0.20+/-0.32 g/day, p=0.016) and the blood pressure (systolic: 133.3+/-18.2 to 123.4+/-10.5 mmHg, p=0.041; diastolic: 79.4+/-11.9 to 72.0+/-8.2 mmHg, p=0.038). Although the global glomerular sclerosis ratio was unchanged (6.3+/-8.5% to 10.7+/-16.1%, p=0.33), the mesangial matrix expansion ratio (33.1+/-10.8% to 22.7+/-7.8%, p=0.001) and the interstitial fibrosis ratio (19.9+/-5.8% to 13.8+/-4.4%, p=0.034) were significantly reduced by ARB treatment. The levels of pathological improvement were similar between patients with IgA nephropathy and those with non-IgA mesangial proliferative glomerulonephritis. The results of the present study strongly suggest that ARB monotherapy can significantly reverse pathological changes, including mesangial matrix expansion and interstitial fibrosis, in human glomerulonephritis.

Upregulation of the brain renin-angiotensin system in rats with chronic renal failure

AIM

We investigated how the brain renin-angiotensin system is involved in regulation of the sympathetic activity and arterial pressure in rats with chronic renal failure.

METHODS

Systolic arterial pressure, heart rate and diurnal urinary noradrenaline excretion were measured for 12 weeks in spontaneously hypertensive rats (SHR) with or without subtotal nephrectomy. Expression of mRNAs related to the brain renin-angiotensin system was measured using polymerase chain reaction. Effects of a 6-day intracerebroventricular infusion of a type 1 angiotensin II receptor antagonist (candesartan) or bilateral dorsal rhizotomy on these variables were also investigated.

RESULTS

Systolic arterial pressure and urinary excretion of noradrenaline were consistently higher in subtotally nephrectomized SHR than in sham-operated SHR (262 +/- 5 vs. 220 +/- 3 mmHg, P < 0.001; 2.71 +/- 0.22 vs. 1.69 +/-0.19 ng g(-1) body weight day(-1), P < 0.001). Expression of renin, angiotensin-converting enzyme and type 1 angiotensin II receptor mRNAs in the hypothalamus and lower brainstem was greater in subtotally nephrectomized SHR than in sham-operated SHR. Continuous intracerebroventricular infusion of candesartan attenuated hypertension and the increase in urinary noradrenaline excretion in subtotally nephrectomized SHR. Dorsal rhizotomy decreased arterial pressure, urinary excretion of noradrenaline and expression of renin-angiotensin system-related mRNAs in brains of subtotally nephrectomized SHR.

CONCLUSION

The brain renin-angiotensin system in subtotally nephrectomized SHR appears to be activated via afferent nerves from the remnant kidney, resulting in sympathetic overactivity and hypertension in this chronic renal failure model.

Effect of fasudil on Rho-kinase and nephropathy in subtotally nephrectomized spontaneously hypertensive rats

BACKGROUND

Although Rho-kinase is reported to play an important role in vascular injury, the contribution of Rho-kinase to the progression of renal injury remains unestablished.

METHODS

We examined the effect of fasudil, a Rho-kinase inhibitor, on the progression of renal injury in subtotally nephrectomized spontaneously hypertensive rats (SHR). Rats were randomly assigned to three groups: sham-operated SHR; salt-loaded subtotally nephrectomized rats (SHR-subtotal nephrectomy); SHR-subtotal nephrectomy given fasudil for 6 weeks (SHR-subtotal nephrectomy + fasudil; 3 mg/kg/day). Renal morphologic and molecular analysis as well as urinary protein excretion was evaluated.

RESULTS

In SHR-subtotal nephrectomy treated with fasudil, systolic blood pressure was not significantly different from that in SHR-subtotal nephrectomy without fasudil (208 +/- 8 mm Hg vs. 217 +/- 14 mm Hg). Urinary protein excretion was markedly increased in SHR-subtotal nephrectomy (124 +/- 16 mg/day), but this increase was significantly suppressed by fasudil (79 +/- 12 mg/day). Renal histologic examination revealed that fasudil improved glomerular and tubulointerstitial injury scores with parallel amelioration of proliferating cell nuclear antigen-positive and ED-1-positive cell infiltration. Furthermore, Western blot analyses showed that both expression and activity of Rho-kinase were enhanced in SHR-subtotal nephrectomy, compared with those in SHR without nephrectomy, and fasudil suppressed Rho-kinase activity. Finally, fasudil up-regulated the expression of p27kip1, a cyclin-dependent kinase inhibitor, and increased the p27kip1 immunopositive cells in both glomeruli and tubulointerstitium with the use of immunohistochemistry.

CONCLUSION

Rho-kinase pathway is involved in the pathogenesis of renal injury. Furthermore, the inhibition of Rho-kinase may constitute a therapeutic strategy for the treatment of renal injury in part through the p27kip1 up-regulation and the subsequent inhibition of cell proliferation and macrophage recruitment.

Combination is better than monotherapy with ACE inhibitor or angiotensin receptor antagonist at recommended doses

OBJECTIVE

The combination of an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II (Ang II) receptor antagonist (ARB) could provide a higher degree of blockade of the renin-angiotensin system(RAS) than either agent alone. The primary aim of this study was to look at the effect of three therapeutic regimens (titrated ACE inhibitor (ACE-I) versus titrated ARB versus the combination of an ACE-I and an ARB) on the attainment of adequate blood pressure (BP) control and antiproteinuric effect. Both ACE-I and ARB were titrated as monotherapy up to the maximal recommended dose.

METHODS

A pilot randomised, parallel group open-label study was conducted in 36 patients with primary renal disease, proteinuria above 1.5 g/day and BP >140/90 mmHg while on therapy with an ACE-I. Patients were randomly assigned to (1) benazepril, n=12; (2) valsartan, n=12; or (3) benazepril plus valsartan, n=12. Other antihypertensive therapies could also be added to attain goal BP (<140/90 mmHg). The primary endpoint was the change in proteinuria during six months of follow-up.

RESULTS

In the presence of similar BP decreases and stable creatinine clearance values, mean proteinuria decreases were 0.5+1.7, 1.2+2.0 and 2.5+1.8 g/day in groups 1, 2 and 3, respectively. When compared with baseline values, only the fall induced by the combination of ARB and ACE-I attained statistical significance (p<0.05).

CONCLUSION

The antiproteinuric capacity of monotherapy at recommended doses with either an ACE-I or an ARB is lower than that obtained with the combination of the two drugs.

Angiotensin receptor blockers in diabetic nephropathy

Where shall we place angiotensin receptor blockers in the scheme of the prevention of diabetic nephropathy? Only the results of a large, randomized double-blind trial with a comparable and appropriate alternative would prove therapeutic efficacy. The results of several trials with angiotensin-converting enzyme (ACE) inhibitors have proven them to be the standard of care for diabetics and their kidneys. As reviewed in this article, the results of three large such clinical trials have recently been completed with angiotensin receptor blockers in patients with type 2 diabetes mellitus. Initial results appear favorable. However, whether angiotensin blockers have more to offer than ACE inhibitors is still speculative. The renin-angiotensin system plays an important role in the pathogenesis of diabetic nephropathy. Since alternative pathways to ACE have been uncovered in the formation of angiotensin II, inhibition at the final end point would provide favored blockade. Because angiotensin receptor blockers do provide this specific blockade, they offer far more promise than ACE inhibitors.

Renoprotective and anti-hypertensive effects of combined valsartan and perindopril in progressive diabetic nephropathy in the transgenic (mRen-2)27 rat

BACKGROUND

We have previously reported that severe glomerulosclerosis progressively develops in the streptozotocin (STZ) diabetic transgenic (mRen-2)27 rat. In this diabetic model, monotherapy with either angiotensin converting enzyme inhibition (ACEI) or angiotensin type 1 (AT(1)) receptor blockade is largely renoprotective. The objective of the present study was to determine if a combination therapy at lower doses than monotherapy would confer greater renoprotection.

METHODS

At 6 weeks of age, non-diabetic control and STZ diabetic female heterozygous Ren-2 rats were randomized to receive vehicle, the AT(1) receptor blocker valsartan (V, 20 mg/kg/day), the ACEI perindopril (P, 6 mg/kg/day), or a combination of low-dose V+P (V, 3 mg/kg/day plus P, 0.5 mg/kg/day) for 12 weeks.

RESULTS

Systolic blood pressure was lowered with all treatments, but the greatest reductions were observed with V monotherapy and combination V+P therapy. All treatments reduced albuminuria, the decline in glomerular filtration rate, and cortical collagen staining, to the same extent. The glomerulosclerotic index was increased with diabetes and reduced with V and P monotherapy. However, the low-dose combination therapy was more effective than single therapy and reduced severe glomerulosclerosis to levels observed in non-diabetic controls.

CONCLUSIONS

Monotherapy with either V or P reduced blood pressure and retarded the decline in renal function and glomerulosclerosis in the diabetic Ren-2 rat. Combination therapy has the additional benefit of requiring only low doses of AT(1) receptor blockade and ACEI to achieve superior renoprotective effects in this diabetic nephropathy model.

Angiotensin type 1 receptor antagonism and ACE inhibition produce similar renoprotection in N(omega)-nitro-L>-arginine methyl ester/spontaneously hypertensive rats

This study was conducted to determine potentially differential effects between an angiotensin II type 1 (AT(1)) receptor antagonist and an ACE inhibitor on systemic, renal, and glomerular hemodynamics and pathological changes in spontaneously hypertensive rats (SHR) with N(omega)-nitro-L>-arginine methyl ester (L-NAME)-exacerbated nephrosclerosis. The hemodynamic, renal micropuncture, and pathological studies were performed in 9 groups of 17-week-old male SHR treated as follows: group 1, controls (n=16); group 2, candesartan (10 mg/kg per day for 3 weeks) (n=7); group 3, enalapril (30 mg/kg per day for 3 weeks) (n=8); group 4, candesartan (5 mg/kg per day) plus enalapril (15 mg/kg per day for 3 weeks) (n=9); group 5, L-NAME (50 mg/L in drinking water for 3 weeks) (n=17); group 6, L-NAME (50 mg/L) plus candesartan (10 mg/kg per day for 3 weeks) (n=7); group 7, L-NAME (50 mg/L) for 3 weeks followed by candesartan (10 mg/kg per day) for another 3 weeks (n=8); group 8, L-NAME (50 mg/L) plus enalapril (30 mg/kg per day for 3 weeks) (n=7); and group 9, L-NAME (50 mg/L) plus enalapril (30 mg/kg per day) and the bradykinin antagonist icatibant (500 microg/kg SC per day via osmotic minipump for 3 weeks) (n=7). Both candesartan and enalapril similarly reduced mean arterial pressure and total peripheral resistance index. These changes were associated with significant decreases in afferent and efferent glomerular arteriolar resistances as well as glomerular capillary pressure. Histopathologically, the glomerular and arterial injury scores were decreased significantly, and left ventricular and aortic masses also were diminished significantly in all treated groups. L-NAME-induced urinary protein excretion was prevented by both candesartan and enalapril. Thus, both AT(1) receptor and ACE inhibition prevented and reversed the pathophysiological alterations of L-NAME-exacerbated nephrosclerosis in SHR. Itatibant only blunted the antihypertensive effects of enalapril but did not attenuate the beneficial effects of ACE inhibition on the L-NAME-induced nephrosclerosis. Thus, the AT(1) receptor antagonism and ACE inhibition have similar renal preventive effects, which most likely were achieved through reduction in the effects of angiotensin II, and ACE inhibition of bradykinin degradation demonstrated little evidence of renoprotection.

Angiotensin II type 1 receptor antagonist versus angiotensin I-converting enzyme inhibitor in experimental renal diseases

Angiotensin II has an important role in the structural and functional regulation of the cardiovascular and renal systems. Blockade of the renin-angiotensin system can be achieved with angiotensin-converting enzyme (ACE) inhibitors and non-peptidic, orally active, angiotensin II type I receptor (AT1) antagonists. However, the question that has yet to be answered is whether ACE inhibitors and AT1 receptor antagonists have similar renoprotective effects in various experimental diseases. Although many studies have assessed the role of either ACE inhibitors or AT1 receptor antagonists, we have reviewed the literature comparing both types of blocker in the same experiment. In most models of hypertension or renal failure, both classes of blocker appear to have similar antihypertensive and renal profiles. In a few models, the influence of the ACE inhibitor on arterial pressure and/or renal function is more marked than that of the AT1 receptor antagonist. Even though the maximum dose-effect curve for each compound was not often carried out for the systemic haemodynamics and renal alterations, the difference between both classes of blocker, when observed, appeared to favour the participation of non-angiotensin II or non-AT1-mediated mechanisms. Among them are the stimulation of prostaglandin production, kinin accumulation, nitric oxide generation and modulation of endothelin or TGFbeta1 expression via direct or indirect pathways. Future experimental and probably human studies aimed at comparing angiotensin II receptor antagonists and ACE inhibitors, with respect to blood pressure and renal damage, should be designed with all these concerns in mind.

Increased gene expression of components of the renin-angiotensin system in glomeruli of genetically hypertensive rats

OBJECTIVE

The renin-angiotensin system (RAS) is implicated in the development of hypertensive glomerulosclerosis. However, no experimental evidence exists that clearly demonstrates activation of glomerular RAS in hypertensive nephropathy. We used stroke-prone spontaneously hypertensive rats (SHRSP) to examine whether RAS components are increased in glomeruli of SHRSP and whether this increase leads to an increase in mRNA levels for transforming growth factor-beta1 (TGF-beta1).

METHODS

We examined the sequential changes of urinary albumin excretion (UAE), morphology, and glomerular mRNA expression for TGF-beta1 and fibronectin (FN) in relation to glomerular mRNA expression for angiotensinogen (ATN), angiotensin converting enzyme (ACE), angiotensin II type 1a (AT1a), and type 1b (AT1b) receptors, and intervention with angiotensin II type 1 receptor antagonist candesartan and equihypotensive hydralazine.

RESULTS

In SHRSP, UAE was normal at 9 weeks of age, but became higher, beginning at 12 weeks of age, than that in the age-matched Wistar-Kyoto (WKY) rats, while SHRSP showed no glomerulosclerosis until 14 weeks of age; it was marked at 24 weeks. Plasma renin activity and plasma angiotensin II level was equivalent in the 9- and 12-week-old SHRSP and the WKY rats; both parameters, however, were elevated in 24-week-old SHRSP as compared with age-matched control. RNase protection assays showed that glomerular levels of ATN, ACE, and AT1a and AT1b receptors mRNA were significantly increased in 9-, 12-, and 14-week-old, but not in 24-week-old SHRSP, compared with age-matched WKY rats. Northern blot analysis showed that glomerular levels of TGF-beta1 and FN mRNA were higher in SHRSP than in WKY rats at all time points. Candesartan reduced UAE to control levels, whereas hydralazine reduced UAE but not to control levels. Candesartan administration for 12 weeks virtually prevented the progression of glomerulosclerosis. While candesartan reduced mRNA levels for RAS components, TGF-beta1, and FN to control levels, hydralazine was not effective in this respect. Conclusion Results suggest that increases in glomerular RAS components that occur independently of circulating RAS alter glomerular permselectivity and increase the glomerular expression of TGF-beta1 and FN in young SHRSP. Findings in old SHRSP suggest that altered glomerular permselectivity and an increased glomerular expression of TGF-beta1 and FN may be associated with the activation of systemic RAS.

Distinct action of aranidipine and its active metabolite on renal arterioles, with special reference to renal protection

Aranidipine, a newly developed calcium antagonist, possesses unique pharmacologic characteristics in that its metabolite (M-1) still has antihypertensive action. We examined the effects of both agents on renal microcirculation using the isolated perfused hydronephrotic rat kidney. During norepinephrine-induced constriction, the addition of aranidipine dilated both afferent and efferent arterioles in a dose-dependent manner; at 10(-6) M, 83 +/- 6% and 90 +/- 6% reversal, respectively. In contrast, its active metabolite exerted dilator action predominantly on the afferent arteriole (79 +/- 4% vs. 44 +/- 17% at 10(-6) M for afferent and efferent arterioles, respectively). We further examined the long-term (8 weeks) effect of these agents on the development of renal injury in salt-loaded subtotally nephrectomized spontaneously hypertensive rats. Both aranidipine and M-1 reduced blood pressure by a similar magnitude. The decreases in proteinuria were observed in the aranidipine-treated group at weeks 6, 8, and 10, whereas in the M-1 group, significant reduction was attained only at week 6. Histopathologic examination revealed that both treatments improved glomerular and arteriolar sclerosis. Glomerular sclerosis, however, was less pronounced in the aranidipine-treated group than in the M-1 group. In conclusion, aranidipine has dilator action on both arterioles, whereas M-1 caused predominant dilation of afferent arterioles. Such metabolic changes may constitute a determinant of efferent arteriolar action of the calcium antagonist.

Renoprotective benefits of RAS inhibition: from ACEI to angiotensin II antagonists

In landmark clinical trials, pharmacological inhibition of the renin-angiotensin system (RAS) with angiotensin-converting enzyme inhibitors (ACEIs) attenuated the decline in renal function associated with chronic renal disease (CRD). Hemodynamic and nonhemodynamic effects of angiotensin II (Ang II) attest to its central role in the pathogenesis of CRD. Angiotensin II subtype 1 receptor antagonists (AT1RA) differ from ACEI in their effects on the RAS and on bradykinin metabolism. Elevations in bradykinin levels associated with ACEI and stimulation of angiotensin subtype 2 receptors resulting from AT1RA may produce therapeutic effects unique to each class of drug. Nevertheless, in animal models of CRD, ACEI and AT1RA exert equivalent renoprotection, implying that their renoprotective effects result primarily from inhibition of Ang II-mediated stimulation of angiotensin subtype 1 receptors. Clinical data comparing ACEI and AT1RA therapy in renal disease are limited to short-term studies, which indicate that AT1RAs have equivalent effects to ACEI on the major determinants of CRD progression, namely blood pressure and proteinuria. AT1RAs were well tolerated, with side-effect profiles similar to placebo. Taken together, available evidence suggests that AT1RAs will share the renoprotective properties of ACEI in human CRD. Nevertheless, the results of long-term clinical trials are required before AT1RA can be recommended as an alternative to ACEI in renoprotective therapy.

Angiotensin-converting enzyme in non-neoplastic kidney diseases

BACKGROUND

The angiotensin I-converting enzyme (ACE, CD143, kininase II) plays a critical role in controlling the level of vasoactive peptides such as angiotensins and kinins in the local circulations and tissue interstitium. Because recent work has documented a vessel-, organ-, and species-specific pattern of endothelial ACE expression in the vascular system, we have analyzed whether or not changes of this pattern occur in vessels, tubules, and interstitium of the human kidney that is affected by different non-neoplastic diseases.

METHODS

Using a set of well-characterized monoclonal antibodies (mAbs), ACE was assessed on renal tissue of 135 patients by immunohistochemistry, including an additional analysis at the ultrastructural level. A semiquantitative evaluation allowed the estimation and comparison of ACE content in different renal compartments. These data were compared with several clinical findings, diagnosis, therapeutic modalities, and histological features.

RESULTS

In contrast to the normal human kidney, where ACE is abundant in the brush border of the proximal tubule but is usually absent in endothelial cells of any vessel type, an endothelial neoexpression of ACE was observed in different diseases. In general, this neoexpression was associated with histological sites of interstitial fibrosis and showed some selectivity for glomerular endothelial cells in diabetes mellitus and chronic arterial hypertension. There was also a loss of epithelial ACE in the proximal tubule in certain pathological conditions, for example, in chronic fibroplastic processes, acute pyelonephritis, and different stages of acute renal failure.

CONCLUSIONS

Neoexpression of ACE by renal endothelial cells, as well as changes of the tubular ACE content, is a common finding in diseased human kidneys. As associated with certain tissue sites, clinical and/or morphological features, these changes may be involved in parenchymal remodeling and renal pathophysiology.

Candesartan cilexetil. A review of its use in essential hypertension

Candesartan cilexetil is completely converted to the nonpeptide angiotensin II receptor blocker candesartan during absorption from the gastrointestinal tract. Candesartan selectively blocks and dissociates slowly from the angiotensin II subtype 1 (AT1) receptor which mediates most of the known activities of angiotensin II. When administered once daily, oral candesartan cilexetil 8 to 32 mg dose-dependently and effectively reduces blood pressure in patients with mild to moderate essential hypertension. In comparative studies, candesartan cilexetil 8 mg/day was as effective as usual therapeutic dosages of enalapril, losartan potassium, hydrochlorothiazide and amlodipine. One study showed candesartan cilexetil 16 mg/day to be more effective than losartan potassium 50 mg/day. Furthermore, the combination of candesartan cilexetil with either hydrochlorothiazide or amlodipine resulted in additive antihypertensive effects. Preliminary evidence suggests that the blood pressure-lowering effects of candesartan cilexetil are associated with the prevention or improvement of end-organ damage in patients with hypertension. However, this requires further confirmation in clinical studies. Candesartan cilexetil improves insulin sensitivity in patients with hypertension and does not affect glucose homeostasis or the serum lipid profile in those with coexisting type 2 (non-insulin-dependent) diabetes mellitus. Candesartan cilexetil is well tolerated in patients with hypertension. Pooled data indicate that the tolerability profile of the drug is not significantly different from that of placebo, with headache being the most commonly reported event. Adverse events are not dose related and are mostly mild to moderate in severity. Candesartan cilexetil is better tolerated than enalapril, primarily because of a reduced incidence of cough, and was not associated with the hypokalaemia or hyperuricaemia seen with hydrochlorothiazide in a study in patients aged > or = 75 years. The drug has an adverse events profile similar to that of losartan potassium in patients with mild to moderate hypertension.

CONCLUSIONS

once daily candesartan cilexetil is effective and well tolerated when used once daily (as monotherapy or in combination with other antihypertensive agents) in patients with mild, moderate or severe hypertension. Initially, however, the drug is likely to be used as an alternative to other agents in patients not responding to or intolerant of their current drug therapy.

Protective effects of valsartan and benazeprilat in salt-loaded stroke-prone spontaneously hypertensive rats

These experiments examined the effectiveness of chronic blockade of the renin angiotensin system with either valsartan or benazeprilat on survival, blood pressure and end-organ damage in salt-loaded stroke-prone SHR. Valsartan or benazeprilat given continuously by subcutaneous osmotic minipump beginning at 10.5 weeks of age lowered blood pressure, as determined by radiotelemetry, prevented proteinuria, prolonged survival and decreased the severity of histopathological changes in the heart and kidney. These results indicate that angiotensin receptor blockade affords a similar degree of protection as inhibition of angiotensin converting enzyme in salt-loaded stroke-prone SHR. Furthermore, our results are consistent with a primary contribution of angiotensin II to the maintenance of blood pressure and support a principal role for angiotensin II-dependent mechanisms in the development of end-organ damage in the salt-loaded stroke-prone SHR.

Ischemic renal diseases: new insights into old entities

Vascular nephropathies are a steadily increasing cause of end-stage renal failure. Arterionephrosclerosis and arteriolonephrosclerosis are common features in the hypertensive patient. This is especially true for blacks of African descent, in whom hypertension and nephrovasculopathies are a major cause of renal insufficiency. That primary hypertension leads to renal vascular lesions, glomerular obsolescence and interstitial fibrosis has long been established. It should not, however, obscure the fact that renal vascular lesions can be observed in animal models as well as in some humans, especially young blacks, in the absence of, or anticipating the onset of hypertension. This leads to considering the hypothesis that nephroangiosclerosis might stem from a genetic defect in the renal vascular bed and that this defect is strongly associated with the hypertensive trait. Atherosclerotic renal disease is a major, potentially treatable cause of chronic renal disease is a major, potentially treatable cause of chronic renal failure, especially in whites. It leads to renal atrophy, but the ischemic kidney retains a vigorous potential for tubular cell regeneration, which pleads for early recognition and treatment. Recent data suggest that renal ischemia, be it due to renal artery stenosis or to cholesterol crystal embolism, ranks among the multiple causes of secondary focal segmental glomerulosclerosis. Irrespective of its initial mechanism, ischemia induces renal fibrosis, the pathophysiology of which is centered on increased generation of angiotensin II. Finally, renal vascular lesions are commonly observed in the course of various nephropathies, even in the absence of hypertension, and the relationship between these lesions and the unfavorable prognosis of glomerulopathies, especially primary focal-segmental glomerulosclerosis, membranous glomerulopathy and IgA glomerulonephritis, remains to be elucidated. Expanding knowledge of the spectrum of nephrovasculopathies opens perspectives for investigating, understanding and treating a major mechanism of progressive renal insufficiency.

Renal protective effects of efonidipine in partially nephrectomized spontaneously hypertensive rats

We investigated the effects of a calcium antagonist, efonidipine, which was reported to dilate not only afferent arterioles but also efferent alterioles, on progression of renal failure in salt-loaded partially nephrectomized spontaneously hypertensive rats (SHR). Forty-four SHR's with 5 of 6 nephrectomy were divided into four groups: group 1 as control (n=20); group 2, efonidipine-treated (n=8); group 3, enalapril-treated (n=8); and group 4, nifedipine-treated (n=8). The rats were given these drugs and a high-salt diet (5% NaCl) for 8 weeks. During the experiment, systolic blood pressure (SBP) and daily urinary protein excretion were measured every 2 weeks. At the end of the study, serum creatinine was determined, and renal tissues were obtained for light microscopic examination. SBP was markedly reduced by 8-week antihypertensive treatment. (control, 267+/-7 mmHg; efonidipine, 181+/-7 mmHg; enalapril, 200+/-12 mmHg; nifedipine, 184+/-6 mmHg). Glomerular sclerosis developed markedly in the control group, but was partially prevented in all treated groups. Similarly, urinary protein excretion (UPE) was suppressed by efonidipine (180+/-16 mg/day) and enalapril (186+/-16 mg/day vs. 301+/-28 mg/day for control). In contrast, nifedipine failed to prevent the increase in urinary protein excretion (258+/-22 mg/day). In conclusion, efonidipine attenuates SBP increase and ameliorates glomerular injury as well as nifedipine and enalapril. Furthermore, beneficial effects of efonidipine, but not nifedipine, on proteinuria suggest that different mechanisms mediate the improvement of proteinuria; one possible mechanism could be efferent arteriolar dilation, not reported in nifedipine.