Effects of benidipine on renal function in anesthetized spontaneously hypertensive rats

Reduced progression of adriamycin nephropathy in spontaneously hypertensive rats treated by losartan

BACKGROUND

The aim of the study was to investigate the antihypertensive effects of angiotensin II type-1 receptor blocker, losartan, and its potential in slowing down renal disease progression in spontaneously hypertensive rats (SHR) with adriamycin (ADR) nephropathy.

METHODS

Six-month-old female SHR were randomly selected in six groups. Two control groups (SH(6), SH(12)) received vehicle. Groups ADR(6), ADR+LOS(6) and ADR(12), and ADR+LOS(12) received ADR (2 mg/kg/b.w. i.v.) twice in a 3-week interval. Group ADR+LOS(6) received losartan (10 mg/kg/b.w./day by gavages) for 6 weeks and group ADR+LOS(12) for 12 weeks after second injection of ADR. Animals were killed after 6 or 12 weeks, respectively. Haemodynamic measurements were performed on anaesthetized animals, blood and urine samples were taken for biochemical analysis and the left kidney was processed for morphological studies.

RESULTS

Short-term losartan treatment, besides antihypertensive effect, improved glomerular filtration rate and ameliorated glomerulosclerosis resulting in decreased proteinuria. Prolonged treatment with losartan showed further reduction of glomerulosclerosis associated with reduced progression of tubular atrophy and interstitial fibrosis, thus preventing heavy proteinuria and chronic renal failure. Losartan reduced uraemia and increased urea clearance in advanced ADR nephropathy in SHR. Histological examination showed that losartan could prevent tubular atrophy, interstitial infiltration and fibrosis in ADR nephropathy.

CONCLUSION

Losartan reduces the rate of progression of ADR-induced focal segmental glomerulosclerosis to end-stage renal disease in SHR.

Pharmacological, Pharmacokinetic, and Clinical Properties of Benidipine Hydrochloride, a Novel, Long-Acting Calcium Channel Blocker

Benidipine is a dihydropyridine-derived calcium channel blocker developed in Japan, with several unique mechanisms of action, that is, triple calcium channels (L, N, and T) blocking action with a membrane approach. Benidipine has relatively high vascular selectivity and is expected to show protective effects on vascular endothelial cells. Renal protective effects of benidipine also have been shown in several basic and clinical studies. Moreover, anti-oxidative action and enhancing nitric oxide production have been noted with this drug, following its cardio-protective effects in patients with ischemic heart diseases. In fact, benidipine exerted a better prognostic effect than other calcium channel blockers in the therapy for patients with vasospastic angina. In addition, benidipine showed reliable antihypertensive, renoprotective effects if used in combination with angiotensin II type 1 receptor blockers (ARBs) when adequate anti-hypertensive effects are not achieved by ARBs alone, indicating that benidipine is an useful calcium channel blocker in combination therapy for hypertension. Benidipine was launched on the Japanese market 14 years ago, but few severe side effects have been reported, suggesting that this is a drug with established safety and long-acting pharmacological effects.

Effects of benidipine on glomerular hemodynamics and proteinuria in patients with nondiabetic nephropathy

Experimental studies suggest that some long-acting calcium antagonists decrease glomerular hypertension and suppress the progression of nephropathy, but clinical evidence is lacking. To investigate clinically whether a long-acting calcium antagonist, benidipine, lowers glomerular capillary hydraulic pressure via a decrease in efferent arteriolar resistance and decreases proteinuria, we examined hypertensive patients with nondiabetic nephropathy. The subjects were 7 patients with chronic glomerulonephritis or glomerulosclerosis. Before and during the administration of benidipine (4 mg/day), systemic pressure, glomerular hemodynamics, the sodium sensitivity index (reciprocal of the pressure-natriuresis curve), and urinary excretion of proteins (total protein, albumin, and immunoglobulin G) were investigated. The glomerular hemodynamics in terms of glomerular capillary hydraulic pressure and resistance of afferent and efferent arterioles were calculated from the renal clearance, plasma total protein concentration, and pressure-natriuresis relationship. Benidipine lowered the mean arterial pressure from 105 +/-5 to 99 +/- 4 mm Hg (p = 0.002; mean +/- SD) and glomerular pressure from 48 +/- 8 to 39 +/- 5 mmHg (p = 0.006) by decreasing the resistance of efferent arterioles. Benidipine made the pressure-natriuresis curve steeper and decreased the median sodium sensitivity index from 0.099 (0.084 and 0.117; 25th and 75th percentiles) to 0.048 (0.017 and 0.058; p = 0.018). Urinary excretion of proteins did not change. Our clinical study showed that benidipine lowered the glomerular pressure by decreasing the resistance of efferent arterioles and decreased the sodium sensitivity of blood pressure, but did not affect proteinuria in patients with nondiabetic nephropathy.

Benidipine dilates both pre- and post-glomerular arteriole in the canine kidney

The aim of the present study was to determine the effects of benidipine on renal function and whether benidipine may dilate the efferent arteriole as well as the afferent arteriole of the canine kidney. The effects of benidipine on the renal segmental vascular resistance were estimated using Gomez's formula with some modification. The renal hemodynamic action of benidipine was also compared with that of amlodipine. Intrarenal arterial injection of benidipine at a dose of 3 microg/kg resulted in a significant increase in renal blood flow (RBF), urine flow and urinary excretion of sodium, but not in glomerular filtration rate (GFR). Amlodipine at a dose of 300 microg/kg also increased RBF, urine flow and urinary excretion of sodium to a significant degree equivalent to that by benidipine. However, in contrast to benidipine, amlodipine significantly increased GFR. After the administration of benidipine, autoregulation of RBF and GFR was relatively maintained and the renal perfusion pressure (RPP)-RBF relation shifted upward; that is, RBFs at 75 and 50 mmHg were maintained at a higher level than those of the control. In contrast to benidipine, amlodipine diminished the autoregulation of RBF and GFR. RBFs at 75 and 50 mmHg were not different from those of the control. The afferent and efferent arteriolar resistance (Ra and Re) were calculated based on the RPP-RBF and RPP-GFR relations. Benidipine reduced both Ra and Re, but amlodipine selectively reduced Ra. Benidipine increased RBF but not GFR via the dilation of both afferent and efferent arterioles. Thus, benidipine has unique renal hemodynamic actions which differ from those by most calcium antagonists.

Regulation of the renal basolateral transport system for organic anions by calcium channel blockers

Calcium channel blockers have been reported to exert multiple effects on renal tubular function. Therefore, the effects of the calcium channel blockers nifedipine and verapamil on the cellular uptake of tritiated para -aminohippuric acid (PAH) into microdissected non-perfused rabbit kidney S2 proximal tubule segments were investigated to study a possible influence of calcium channel blockers on renal PAH transport. Since the tubules were entirely collapsed, the accumulated radioactivity overwhelmingly reflects the transport across the basolateral membrane. Tubular PAH accumulation was increased by 1 and 10 microm verapamil, and by 1 microm nifedipine, but it was unaffected by lower or higher concentrations of these calcium channel blockers. The increase in PAH accumulation caused by 1 microm nifedipine or 10 microm verapamil was independent from changes in intracellular Ca(2+) and inhibited by staurosporine (1 and 10 n m) a potent inhibitor of protein kinase C (PKC). Our results indicate that the calcium channel blockers nifedipine and verapamil increase the transport of organic anions across the basolateral membrane of proximal tubules, probably by an activation of PKC. Furthermore, the increased tubular PAH transport may disturb the estimation of the renal PAH-clearance.

Renal effects of the calcium channel blocker aranidipine and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats

The purpose of this study was to investigate the renal effects of aranidipine, a novel calcium channel blocker of the dihydropyridine type, and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats (SHRs). When infused into the renal artery in anesthetized dogs, aranidipine (0.03 microg/kg/min) induced sustained increases in urine volume and urinary excretion of sodium and of potassium. This effect was greater than that elicited by nifedipine (0.1 microg/kg/min). The aranidipine metabolite, M-1 (0.1 microg/kg/min), also caused diuresis and natriuresis almost equal to those of nifedipine. The stop-flow experiment using the anesthetized dog showed that intrarenal infusion of aranidipine (0.03 microg/kg/min), as well as nifedipine (0.1 microg/kg/min), produced natriuresis at the distal tubular site rather than at the proximal site. Aranidipine (0.3, 1, and 3 mg/kg), when administered orally, dose-dependently increased urine volume and urinary excretion of electrolytes in conscious saline-loaded SHRs. M-1 (10 mg/kg, p.o.) also showed diuretic and natriuretic effects comparable to those of nifedipine (10 mg/kg) in SHRs. In addition, after repeated oral administration of aranidipine for 7 days, short-term tolerance was not found for its diuretic and natriuretic effects in SHRs. These results suggest that, apart from antihypertensive efficiency, aranidipine may offer a therapeutic advantage by producing diuresis and natriuresis in hypertensive patients. The metabolite of aranidipine may contribute, in part, to the diuretic, natriuretic, and antihypertensive effects of aranidipine.

Suppressive effects of benidipine on the development of hypertension and renal lesions in salt-loaded stroke-prone spontaneously hypertensive rats

1. The effects of benidipine hydrochloride (benidipine), a long-acting dihydropyridine calcium antagonist, on the development of hypertension and renal lesions were examined in stroke-prone spontaneously hypertensive rats (SHRSP). 2. SHRSP were fed with 8% NaCl diet for 3 weeks from 13 weeks of age, and benidipine (1 or 3 mg/kg per day) was orally administered during the same period. 3. The high salt diet accelerated an increase in urinary excretions of total protein and albumin, and caused marked arteriole, glomerular and tubular lesions in the kidney. 4. Benidipine significantly inhibited these changes, and also suppressed the elevation of blood pressure in salt-loaded SHRSP. 5. These results reveal that benidipine has protective effects against the development of hypertension and the progression of renal lesions induced by the high salt diet in SHRSP.