Abstract
The relaxant action of vasoactive intestinal peptide (VIP) was investigated using helical strips of four major branches of bovine coronary arteries. The concentration of VIP causing 50 percent of maximal relaxation ranged from 23 to 90 nM. Preincubation of arterial strips with VIP shifted the concentration-response curves for contractions elicited by potassium chloride or prostaglandin F 2α to the right. The relaxant effect of VIP was retained following removal of the vascular endothelium or in the absence of extracellular calcium. The structurally homologous peptides porcine and human peptide histidine isoleucine (PHI) were less potent than was VIP. It is concluded that there are functional receptors for VIP in bovine coronary arteries.
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