Vasoactive intestinal peptide in man: pharmacokinetics, metabolic and circulatory effects.

Graded doses of 0.6, 1.3, and 3.3 pmol/kg/min of vasoactive intestinal peptide (VIP) were intravenously infused over 30 minute periods in four healthy volunteers and plasma VIP levels were measured by radioimmunoassay. Even with the smallest dose of VIP, plasma concentrations rose markedly above normal values. Infusion of higher VIP doses resulted in mean plateau levels of circulating VIP which were in the range of VIP values found in the Verner-Morrison syndrome. After cessation of the VIP infusions, plasma VIP levels fell strikingly by first order kinetics with an average disappearance half-time of one minute. The apparent metabolic clearance rate was about 9 ml/kg/min and the apparent volume of distribution for VIP was approximately 14 ml/kg. During infusion of the highest VIP dose, previously shown to induce one-fifth maximum pancreatic juice secretion, plasma concentrations of glucose, free fatty acids, and calcium were slightly but significantly raised, the pulse rate and the amplitude of blood pressure were increased, and cutaneous flushing occurred. The spectrum of effects accords well with some abnormalities seen in the Verner-Morrison syndrome. The present data, however, do not support a role for VIP as a circulating hormone, at least under physiological conditions.