The regulatory effect of substances released from porcine bronchial epithelial cells on hypoxic pulmonary vasoconstriction.

In this study, porcine pulmonary artery segments (intact or denuded) and bronchial segments (with or without epithelium) were tested in organ bath. Hypoxia caused a bronchial epithelium dependent relaxation of intact or denuded pulmonary artery preconstricted with phenylephrine. Constriction in intact pulmonary artery coated with epithelium denuded bronchus was observed during hypoxia. The bronchial epithelium-dependent relaxation could be inhibited by indomethacin but not be blocked by the following agents: atropine, propranolol, gossypol, methylene blue and chlorpheniramine. The results suggested that HPV was endothelium-dependent. Hypoxia could cause the production of an epithelium-derived relaxing factor (EpDRF), which acted directly on smooth muscle. The effect of EpDRF was not mediated by pulmonary endothelium, but might be related to arachidonic acid cyclooxygenase pathway.