Abstract
The purpose of this study was to evaluate the constrictive effect of endothelin, a peptide vasoconstrictor derived from endothelium, on canine basilar artery. Constriction was measured by an isometric tension recording method. Endothelin induced prolonged contraction of canine basilar artery in a dosedependent fashion, the estimated concentration at 50% contraction being (2.1 ± 0.5) × 10-9 M (mean ± SEM). Removal of endothelium significantly augmented the arterial response to endothelin. In Ca++-free medium no contractile response was elicited at 10-8 M endothelin. Papaverine (10-4M) and nicardipine (10-8 M), a calcium channel blocker, almost completely inhibited the contraction induced by 10-8 M endothelin. Pretreatment with nicardipine (10-8-10-6 M) also significantly suppressed the response to endothelin. Acetylcholine (10-7-10-4M), adenosine triphosphate (10-7-10-5M), and thrombin (0.1 and 1.0 U/ml) dose-dependently inhibited contraction of canine basilar artery in response to 3 × 10-9M endothelin. These results show that endothelin has a potent constrictive effect on canine basilar artery and suggest that this substance may play an important role in the pathogenesis of vasospasm following subarachnoid hemorrhage.
