Effect of the vascular endothelium on norepinephrine-induced contractions in uterine radial arteries from the nonpregnant and pregnant human uterus |
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Authors: | SC Steele AY Warren IR Johnson |
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Affiliation: | Department of Obstetrics and Gynaecology, City Hospital, Nottingham, England. |
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Abstract: | 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. STUDY DESIGN: 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. |
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