Plasma from women with pre-eclampsia induces an in vitro alteration in theendothelium-dependent behaviour of myometrial resistance arteries

Objective: To compare the in vitro effect of plasma from normal pregnant wo men 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 d elivered by elective caesarean section at term. Plasma was collected from n ulliparous women with pre-eclampsia (n = 18), and from multiparous normal p regnant women (n = 18), ail samples bring matched for maternal age and gest ation at venepuncture. Pools of plasma from women with pre-eclampsia and no rmal pregnant women were formed from these samples and were used in all the experiments. Methods: Myometrial resistance vessels obtained from the uterine biopsies w ere incubated with normal pregnant plasma, plasma from women with pre-eclam psia, 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 f rom normal pregnant women or without plasma. This alteration in endothelial function occurred after an incubation period of one hour and required a th reshold concentration for its effect to become established. Removal of the vascular endothelium abolished these changes in vessel behav lour. There we re no plasma-induced alterations in the endothelium-independent behaviour o f the vascular smooth muscle. Conclusions: This study supports the hypothesis that plasma from women with pre-eclampsia is capable of altering endothelium-dependent myometrial rela xation in vessels from pregnant women.