Effects of a calcium channel blocker, nicardipine, on pressure-natriuresis in Dahl salt-sensitive rats.

The effects of a calcium channel blocker, nicardipine, on pressure-natriuresis responses were studied in Dahl salt sensitive (DS) and resistant (DR) rats. Differences in the neural and endocrine background were minimized by renal denervation and by holding plasma vasopressin, aldosterone, corticosterone, and norepinephrine levels constant by intravenous infusion. The renal plasma flow (RPF) and glomerular filtration rate (GFR) of DS rats were disautoregulated in the low renal perfusion pressure range, while those of DR rats were autoregulated. Administration of nicardipine (0.3 microgram/kg/min) into the renal artery significantly increased RPF and GFR and abolished the autoregulation in both strains of rats. Nicardipine also sharpened the pressure-natriuresis responses in both strains without changes in fractional excretion of sodium. These findings suggest that nicardipine increased GFR and thereby improved the pressure-natriuresis responses of DS rats.