title: Vasoactive intestinal peptide in bovine pulmonary artery: localisation, function and receptor autoradiography.
abstract: 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. VIP-immunoreactive nerve fibres were present at the adventitial-medial junction and in the media of the vessels. 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 X 10(-9)M. VIP effects did not depend on the presence of intact endothelial cells. 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. 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.
mesh_terms: D000818:Animals; D001345:Autoradiography; D002417:Cattle; D007120:Immunochemistry; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology; D011964:Receptors, Gastrointestinal Hormone / Q000032:analysis*; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide / Q000032:analysis / Q000502:physiology*
chemical_list: D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide