Comparative pharmacology of rat and porcine endothelin in rat aorta and pulmonary artery.

Endothelins are potent vasoactive polypeptides produced by endothelial cells. This study compared the potency and efficacy of porcine and rat endothelin in rat aortic and pulmonary artery rings. We found that porcine endothelin was 25 to 55 times more potent than rat endothelin in both endothelium-intact and -denuded rings. Removal of the endothelium augmented and acetylcholine reduced contraction by either endothelin. We conclude that porcine endothelin is intrinsically more potent than rat endothelin and that the endothelium modulates the contraction of both endothelins.