Cholinergic properties of the bronchial artery and contribution of the endothelium.

Using selective agonists and antagonists, both muscarinic and nicotinic receptors were identified in the bovine bronchial artery. The helical bronchial artery strips contracted to acetylcholine and methacholine and responses to both were blocked by atropine. Nicotine contractions were blocked by both atropine and hexamethonium. Longitudinal strips responded poorly to both acetylcholine and nicotine. Sixty-five percent of pre-contracted bronchial arterial strips with intact endothelium relaxed in the presence of low concentrations of acetylcholine (1 X 10(-9)M to 1 X 10(-7)M), while those strips without endothelium did not. The presence or absence of endothelium was shown histologically, as was the identification of cholinergic fibers located in the adventitia and outer layers of the tunica media of the bronchial artery. These data confirm the hypothesis of vagal innervation of the bronchial artery and also suggest a role for the endothelium in modulating this artery's response to acetylcholine stimulation in obstructive airway diseases.