Influence of calcium entry blockers and calmodulin inhibitors on 5-hydroxytryptamine-, potassium- and calcium-induced contractions in human umbilical artery in-vitro.
The effects of calcium (Ca2+) withdrawal, Ca2+ entry blockers and calmodulin inhibitors on the contractile responses to 5-hydroxytryptamine (5-HT), K+ and CaCl2 have been studied in human isolated umbilical artery. Following Ca2+ withdrawal from the medium (30 min), both 5-HT- and K(+)-induced contractions were virtually abolished. Ca2+ entry blockers (nifedipine, verapamil, diltiazem and cinnarizine) were significantly more effective in inhibiting 5-HT- than K(+)-induced contractions. In relation to calmodulin inhibitors, trifluoperazine inhibited all types of contractions, whereas W-7 (N-6-aminohexyl-5-chloro-1-naphthalene sulphonamide) only inhibited 5-HT- and CaCl2-induced contractions. All drugs inhibited CaCl2-induced contractions in a non-competitive manner. These findings indicate that the mechanisms by which these drugs exert their inhibitory effects on human umbilical artery are markedly different from those reported in other vascular beds.
Department of Pharmacology, CCB, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
Y S
YS
Medeiros
J B
JB
Calixto
D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D014469:Umbilical Arteries / Q000187:drug effects
D002121:Calcium Channel Blockers; D002147:Calmodulin; D012701:Serotonin; D011188:Potassium; D002118:Calcium