Vasoactive peptides in the lung, with special reference to vasoactive intestinal peptide.

Numerous biologically active peptides are present in normal lung. Some of these, like vasoactive intestinal peptide (VIP) and substance P, are neuropeptides that may function as neurotransmitters or neuromodulators. The activities of lung peptides include relaxation or contraction of airway and pulmonary vascular smooth muscle, modification of bronchial water and mucus secretion, and stimulation of adenylate cyclase activity. Much remains to be learned about active peptides in the lung: their full identities, their localization, their physiologic roles, and their participation in disease processes. One of these peptides, VIP, widely distributed in other organ systems, may mediate the nonadrenergic relaxation of airways and pulmonary vessels. It may also regulate bronchial secretion and, through its promotion of cyclic adenosine monophosphate accumulation in the lung, may modulate the immunologic release of mediators from mast cells.