Endothelin contracts human uterine myometrium by a partly dihydropyridine-sensitive mechanism.
The effect of endothelin (ET), a recently discovered 21-amino-acid polypeptide with powerful vasoconstrictor properties, was examined on human uterine myometrial strips in vitro. ET dose-dependently (10(-11)-10(-7) M) increased the contractile force (monitored as contraction amplitude) of the myometrium with significant effects at 10(-8) and 10(-7) M. ET (10(-8) M and up) also increased the basal tone of the myometrium. The calcium channel blocking agents nifedipine (10(-7) M) and diltiazem (10(-6) M) both inhibited the spontaneous tonic contractions of the myometrium. When ET was given in the presence of nifedipine, the tonic contractions were further inhibited, whereas the ET-induced increase in basal tone remained. The same result was obtained with diltiazem (10(-6) M). The results indicate that the contractility of human myometrium may be modulated by ET, and that the effects of ET on the human myometrium are only partly mediated by dihydropyridine-sensitive calcium channels.
Fried
G
G
Department of Obstetrics and Gynaecology, Karolinska Institutet, Stockholm, Sweden.
Liu
Y A
YA
Andersson
E
E
D004095:Dihydropyridines / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology; D016232:Endothelins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008875:Middle Aged; D009215:Myometrium / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects*
D004095:Dihydropyridines; D016232:Endothelins; D004110:Diltiazem; D009543:Nifedipine