Vasoactive intestinal polypeptide is more potent than prostaglandin E2 as a vasodilator and oedema potentiator in rabbit skin.

1 The 28 amino acid polypeptide, vasoactive intestinal polypeptide (VIP) induced increased local blood flow when injected intradermally in the rabbit. 2 VIP was found to be even more potent than prostaglandin E2 (PGE2) in increasing blood flow; VIP induced a significant effect at a 1 pmol dose. 3 VIP was shown to be poor in increasing microvascular permeability but very potent in enhancing local oedema induced by two substances which increase permeability, bradykinin and C5a des Arg. VIP was more potent than PGE2 as an oedema potentiator. 4 Indomethacin had no effect on oedema potentiation induced by VIP, suggesting that a release of endogenous prostaglandins was not involved. 5 These results support our hypothesis for the regulation of oedema formation by arteriolar vasodilators, although the observations do not exclude the possibility of additional regulation by agonist interaction in the region of the venule. 6 VIP may be involved in the physiological control of normal blood flow and in hyperaemia in some types of inflammatory reactions.