Pulmonary vasoactivity of lung endocrine cell-related peptides

Lung endocrine-like cells are believed to contain three immunohistochemically distinct peptides: bombesin, calcitonin, and Leu-enkephalin. Because these peptides exhibit smooth muscle stimulatory or inhibitory activity in some tissues, it has been suggested that their release from endocrine-like cells may influence airway or pulmonary vascular smooth muscle tone. To determine whether lung endocrine cell-related peptides could exert a regulatory influence in the pulmonary circulation, we evaluated their ability to constrict or dilate the vasculature of isolated perfused rat lungs. Neither bombesin nor calcitonin exhibited any pulmonary vascular effects. However, Leu-enkephalin provoked dose-dependent pulmonary vasoconstriction. These results suggest that Leu-enkephalin released from lung endocrine-like cells could be involved with regulation of pulmonary vascular tone.