Endothelium-dependent relaxation of human basilar arteries.

We studied the effects of acetylcholine and calcium ionophore A23187 on human basilar artery rings. Among 11 arteries, both agents produced significant relaxations in five, A23187 but not acetylcholine caused a response in six, and neither agent was effective in four. After rubbing off the endothelium, the relaxations induced by both agents were significantly attenuated. Indomethacin (a cyclooxygenase inhibitor) and AA861 (a specific inhibitor of 5-lipoxygenase) did not but SKF525A (an inhibitor of cytochrome P450-dependent monooxygenase) did significantly inhibit the acetylcholine-induced relaxation in human basilar arteries. On the other hand, AA861 inhibited while neither indomethacin nor SKF525A had any effect on the A23187-induced relaxation. Our results suggest that different mechanisms may be involved in acetylcholine and A23187-induced relaxations in human basilar arteries.