Glomerular hemodynamics of the clipped kidney: effects of captopril and diltiazem.

Glomerular hemodynamics of the clipped kidney in two kidney-one clip Goldblatt-hypertensive rats were studied by micropuncture techniques after administration of either captopril (20 mg/kg of b.wt./day p.o.) or diltiazem (3 mg/kg of b.wt./hr i.v.). Both drugs decreased mean arterial and poststenotic renal arterial pressure to comparable levels. Total kidney glomerular filtration rate was not significantly different in the three groups (0.78 +/- 0.09 in hypertensive controls, 0.62 +/- 0.11 after captopril and 0.74 +/- 0.07 ml/min/g of kidney weight after diltiazem). Glomerular capillary pressure fell significantly in both treated groups but was lower in captopril-treated animals (60 +/- 2 in hypertensive controls, 45 +/- 2 after captopril and 53 +/- 1 mm Hg after diltiazem, both P < .05 vs. hypertensive controls). Afferent arteriolar resistance was lowered in both treatment groups to the same extent, whereas only captopril decreased efferent arteriolar resistance. Single nephron filtration rate of cortical nephrons was not altered significantly by captopril due to a 96% increase in the ultrafiltration coefficient and a 58% rise in glomerular plasma flow, whereas diltiazem increased ultrafiltration coefficient by 62% but did not affect glomerular plasma flow. These studies indicate that, despite of decreased effective filtration pressure, glomerular filtration rate is well preserved after converting enzyme inhibition. Captopril and diltiazem have different effects on glomerular hemodynamics within the stenosed kidney.