✓ The effect of endothelium removal on the contractile responses to KCl, hemoglobin, serotonin (5-HT), norepinephrine (NE), prostaglandin (PG)F2α, PGD2, and PGE2 was investigated in canine and rabbit basilar arteries by an isometric tension-recording method. In canine basilar arteries, endothelium removal elevated the dose-response curves to 5-HT, PGF2α, and PGD2, and PGE2, but not to KCl, hemoglobin, or NE. In rabbit basilar arteries, on the other hand, removal of the endothelium elevated the dose-response curves to 5-HT, NE, PGF2α, and PGD2, but not to KCl or hemoglobin. Neither contractile nor inhibitory response was elicited by PGE2 in rabbit basilar arteries. Contraction induced by 5-HT and NE following endothelium removal had a much more pronounced effect in rabbit basilar arteries than in canine basilar arteries.
These results suggest that, following endothelium removal, abolition of the spontaneous release of endothelium-derived relaxing factor is the most probable mechanism of the enhanced vasocontraction. Since endothelial damage results from subarachnoid hemorrhage, the aforementioned mechanism of vasocontractile enhancement may play a role in the pathogenesis of cerebral vasospasm.