Plasma from women with pre‐eclampsia induces an in vitro alteration in the endothelium‐dependent behaviour of myometrial resistance arteries

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Abstract
Objective To compare the in vitro effect of plasma from normal pregnant women and women with pre‐eclampsia on the endothelium‐dependent behaviour of myometrial resistance arteries from normal pregnant women. Design An in vitro comparative study. Setting Nottingham City Hospital. Sample Uterine biopsy specimens were obtained from normal pregnant women delivered by elective caesarean section at term. Plasma was collected from nulliparous women with pre‐eclampsia (n= 18), and from multiparous normal pregnant women (n= 18), all samples being matched for maternal age and gestation at venepuncture. Pools of plasma from women with pre‐eclampsia and normal pregnant women were formed from these samples and were used in all the experiments. Methods Myometrial resistance vessels obtained from the uterine biopsies were incubated with normal pregnant plasma, plasma from women with pre‐eclampsia, or without plasma. Wire myography was employed to study the effect of plasma on the endothelium‐dependent behaviour of these vessels. Results Incubation of vessels from normal pregnant women with plasma from women with pre‐eclampsia resulted in a significant reduction in endothelium‐dependent relaxation, compared with vessels incubated either with plasma from normal pregnant women or without plasma. This alteration in endothelial function occurred after an incubation period of one hour and required a threshold concentration for its effect to become established. Removal of the vascular endothelium abolished these changes in vessel behaviour. There were no plasma‐induced alterations in the endothelium‐independent behaviour of the vascular smooth muscle. Conclusions This study supports the hypothesis that plasma from women with pre‐eclampsia is capable of altering endothelium‐dependent myometrial relaxation in vessels from pregnant women.