Effects of Bay K 8644 on 45Ca uptake and efflux and on contraction in the rabbit aorta.
Contractions induced by K+, noradrenaline and 11,9-epoxymethano prostaglandin H2 (11,9-epoxymethano PGH2) were accompanied by a large, moderate and negligible stimulation of 45Ca uptake in rabbit aortic rings, respectively. Bay K 8644, 14 and 56 nM, enhanced both the contraction and the 45Ca uptake stimulated by all 3 agonists. In the absence of agonists, Bay K 8644 (14 and 56 nM) caused a small contraction and increase in 45Ca uptake. 45Ca efflux was increased by noradrenaline, and Bay K 8644 augmented this. In Ca-free solution, contractions induced by noradrenaline or 11,9-epoxymethano PGH2 were not augmented by Bay K 8644. Nifedipine (0.1 microM) antagonized 45Ca uptake stimulated by K+ or noradrenaline. Nifedipine also reduced the stimulant effect of Bay K 8644 on 45Ca uptake in the presence of all three agonists. It is concluded that, in the rabbit aorta, Bay K 8644 enhances the opening of Ca channels both during depolarization and in the presence of receptor-specific agonists and is also able to open Ca channels under basal conditions. Bay K 8644 appears not to reduce Ca efflux or enhance Ca release from intracellular stores.
Y J
YJ
Dong
R M
RM
Wadsworth
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D066298:In Vitro Techniques; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects*
D002132:Calcium Radioisotopes; D011450:Prostaglandin Endoperoxides, Synthetic; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D009543:Nifedipine; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine