Effects of calcium entry blockers on KCl- and 5-hydroxytryptamine-induced contractions of human umbilical arteries.
The effects of Ca2+ removal and of the calcium entry blockers, nicardipine and nifedipine, on contractions of isolated human umbilical arteries, elicited with KCl and 5-hydroxytryptamine, were investigated. Withdrawal of Ca2+ caused inhibition of both KCl and 5-hydroxytryptamine responses, but the maximum effect of KCl in Ca2(+)-free medium was recuperated by increasing the KCl concentration. The maximum effect of 5-hydroxytryptamine, however, was recuperated only when Ca2+ was restored to the medium. Consistently with an inhibition in Ca2(+)-free medium, calcium entry blockers produced a concentration-dependent relaxation of human umbilical artery strips precontracted with KCl and 5-hydroxytryptamine, and inhibited the concentration-dependent contraction elicited by these stimuli. Our results indicate that contractile responses of the human umbilical arteries are dependent on extracellular Ca2+ for both KCl and 5-hydroxytryptamine. Although Ca2+ entry was sensitive to both nicardipine and nifedipine, the differences between the effects of these dihydropyridines with the two experimental approaches we used were not always conclusive.
Salom
J B
JB
Centro de Investigación, Hospital La Fe, Valencia, Spain.
Campos
V
V
Perales
A
A
Torregrosa
G
G
Miranda
F J
FJ
Alabadi
J A
JA
Alborch
E
E
D002121:Calcium Channel Blockers / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009529:Nicardipine / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D014469:Umbilical Arteries / Q000187:drug effects
D002121:Calcium Channel Blockers; D012701:Serotonin; D011189:Potassium Chloride; D009529:Nicardipine; D009543:Nifedipine