Vasoactive intestinal peptide in bovine pulmonary artery: localisation, function and receptor autoradiography

Open Access
Publisher Website
Google Scholar
Abstract
1 The role of vasoactive intestinal peptide (VIP) in the control of pulmonary vascular tone was investigated by functional response, immunocytochemical localisation and receptor autoradiography in bovine pulmonary arteries. 2 VIP-immunoreactive nerve fibres were present at the adventitial-medial junction and in the media of the vessels. 3 Exposure of precontracted bovine pulmonary artery segments to VIP in vitro resulted in almost complete (86 ± 3%; mean ± s.e.mean) relaxation, the concentration needed for 50% relaxation being 4.47 ± 0.37 × 10−9 M. VIP effects did not depend on the presence of intact endothelial cells. 4 The distribution of VIP receptors was studied by autoradiography using [125I]-VIP. A high density of VIP receptors was found in arterial vascular smooth muscle, with a gradient of density from adventitia to luminal surface. There were no receptors on endothelial cells. 5 These data show that VIP is a potent vasodilator of bovine pulmonary arteries, via direct activation of VIP receptors in vascular smooth muscle. VIP-immunoreactive nerves may influence pulmonary vascular tone directly and could, therefore, be important in regulating pulmonary blood flow.