Effects of vasoactive intestinal polypeptide (VIP) on renal function and plasma renin activity in the conscious rabbit.

Conscious rabbits received either vasoactive intestinal polypeptide (VIP) at a dose of 1, 10 or 25 pmol kg-1 min-1 or vehicle alone (control) through an ear vein for 2 h. Experimental design followed a randomized Latin square arrangement. VIP led to a decrease in effective renal plasma flow and glomerular filtration rate (P less than 0.01) during infusion of the middle and high doses. Mean arterial blood pressure rose slightly (P less than 0.05) and filtration fraction increased (P less than 0.01) during infusion of the middle dose. The high dose produced a rise in heart rate, a fall in plasma sodium, potassium and phosphate concentrations and a rise in plasma solids (P less than 0.01). In spite of the renal haemodynamic effects and changes in plasma composition during infusion of the high dose, fractional excretion of sodium, potassium and chloride doubled (P less than 0.05), suggesting a direct action of VIP on renal tubular function. Plasma renin activity increased between 2- and 3-fold (P less than 0.01). The mechanism of the renin response is uncertain. These results, together with the reported presence of VIP-like material in the renal cortex, may indicate a role for VIP in the regulation of renal function, including renin release.