Effect of the vascular endothelium on norepinephrine-induced contractions in uterine radial arteries from the nonpregnant and pregnant human uterus.
OBJECTIVE
Our purpose was to investigate the role of the endothelium in the human uterine arterial response to norepinephrine in the nonpregnant and pregnant states.


METHODS
Tissue was obtained from six pregnant and six nonpregnant women undergoing cesarean section or hysterectomy. Uterine radial arteries were isolated and subjected to norepinephrine dose-response curves with and without intact endothelium.


RESULTS
Responses were obtained over a dose range of 10(-8) to 10(-4) norepinephrine. Initially there was no difference between vessels from pregnant and nonpregnant patients, but removal of the endothelium significantly increased the response in vessels from pregnant women. Addition of nitro-L-arginine methyl ester when the endothelium was intact did not alter the dose-response curves.


CONCLUSIONS
In pregnancy human uterine radial arteries are more sensitive to norepinephrine than during the nonpregnant state. This increase is countered by an endothelium-derived relaxing factor. The factor is unlikely to be nitric oxide.
Department of Obstetrics and Gynaecology, City Hospital, Nottingham, England.
S C
SC
Steele
A Y
AY
Warren
I R
IR
Johnson
D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001158:Arteries / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006801:Humans; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D011247:Pregnancy; D014599:Uterus / Q000098:blood supply*
D001120:Arginine; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine