抄録
Vascular responses to acetylcholine (ACh) and calcium ionophore A23187 were characterized in the rings of canine basilar artery. In preparations precontracted to a stable plateau by 3×10-7 M 5-hydroxytryptamine or 3×10-6 M prostaglandin F2α, A23187 (10-9-10-7 M) elicited significant relaxation of the basilar rings when the endothelium was intact. The ability of a ring to relax in this manner depends upon the presence of the endothelium, according to the evidence obtained by scanning electron microscopy, and the same concentration of A23187 did not relax vascular tissues in which the endothelium was artificially disrupted. On the other hand, ACh (10-7-10-3 M) produced negligible relaxation of canine basilar artery with intact endothelium. Indomethacin pretreatment (1.5×10-5 M) did not affect the A23187-induced relaxation, whereas preincubation with the lipoxygenase inhibitors nordihydroguaiaretic acid (1.5×10-5 M) and AA861 (10-5 M) prevented its relaxant effect. These results suggest that endothelium-dependent relaxation of canine basilar artery by A23187 may be mediated by one or more noncyclooxygenase metabolites.
