Cellular calcium and the contraction induced by prostaglandin F2 alpha in feline cerebral arteries.
The influences of different calcium-entry blockers, sialidase and caffeine on the biphasic contraction induced by prostaglandin (PG) F2 alpha in the feline basilar artery (BA) were studied in calcium-free medium. After incubation in calcium-free solution, PGF2 alpha induced a contraction of the BA amounting to 87% of the contraction in calcium-containing solution. The response was biphasic in 41 out of 42 vessel segments. PGF2 alpha-induced contractions were markedly attenuated in TRIS-buffered solutions as compared to contractions in Krebs solution. PGF2 alpha failed to induce a biphasic contraction (8 out of 9 preparations) in calcium-free HEPES-buffered solution. Calcium entry blockade with 1 mM manganese or 10(-5) M diltiazem abolished the second and major phase of the PGF2 alpha-induced contraction in calcium-free Krebs solution. The second contraction phase was also eliminated in four out of five preparations pretreated with sialidase (1 unit/ml for 30 min.), but was unaffected by a brief exposure to 20 mM caffeine in calcium-free medium. The present findings strongly support previous suggestions that a major part of the PGF2 alpha-induced contraction in calcium-free medium is mediated via the release of calcium bound to the exterior aspect of the cell membrane.
D000818:Animals; D002021:Buffers; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002415:Cats; D002536:Cerebral Arteries / Q000187:drug effects*; D004110:Diltiazem / Q000494:pharmacology; D015237:Dinoprost; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D008345:Manganese / Q000494:pharmacology; D009439:Neuraminidase / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*
D002021:Buffers; D002121:Calcium Channel Blockers; D011460:Prostaglandins F; D002110:Caffeine; D008345:Manganese; D004533:Egtazic Acid; D015237:Dinoprost; D009439:Neuraminidase; D004110:Diltiazem; D002118:Calcium