Vasoactive intestinal peptide relaxes isolated strips of human bronchus, pulmonary artery, and lung parenchyma.

VIP, an endogenous neuropeptide normally present in lungs and other organs, relaxes isolated strips of human bronchus, pulmonary artery, and lung parenchyma in vitro. Pretreatment of these tissues with indomethacin (1 micrograms/ml) markedly enhances the basal tone and the relaxant effect of VIP. The VIP-induced relaxation, especially of pulmonary artery, has a long duration. As a relaxant of human pulmonary arterial strip, VIP is approximately 200 times as potent as prostacyclin, on a molar basis. The results suggest a possible role for VIP as a modulator of airway and pulmonary vascular tone, and as a potential bronchodilator and pulmonary vasodilator in human subjects.