Effects of a calcium antagonist and an angiotensin II receptor antagonist on rat renal arterioles.

The objective of this study was to investigate the effects of a dihydropyridine calcium antagonist, manidipine HCl, and an angiotensin II receptor antagonist, CV-11974, on renal microvasculature in hypertensive rats. Hydronephrosis was induced by ligation of the left ureter in 8-week-old stroke-prone spontaneously hypertensive rats. Two months after the operation, the hydronephrotic kidney was split longitudinally and spread out as a thin sheet, and the renal microvasculature was observed directly under a light microscope. Administration of manidipine HCl (20 micrograms/kg) caused a gradual fall in blood pressure (-34 mmHg). The afferent arterioles were dilated, and maintained the same level of dilatation until 30 min (+20%). The efferent arterioles were also dilated (+8%). Glomerular blood flow was significantly increased (+38%). Administration of CV-11974 (100 micrograms/kg) caused a sharp fall in blood pressure at 2 min (-24 mmHg), with a continuous fall in blood pressure until 60 min (-46 mmHg). The afferent arterioles were gradually dilated (+15%). The efferent arteriole was also dilated until 60 min, but to a lesser extent than the afferent arteriole. Glomerular blood flow was immediately increased (+35%). We conclude that both manidipine HCl and CV-11974 dilated both the afferent and efferent arterioles and increased glomerular blood flow.