Loss of endothelium‐dependent relaxation in myometrial resistance arteries in pre‐eclampsia

Objective To measure endothelium‐dependent relaxation in myometrial resistance arteries and to compare this parameter in nonpregnant and normotensive pregnant women and those with pregnancies complicated by pre‐eclampsia. Design A prospective study. Setting Nottingham City Hospital. Sample Thirty‐seven nonpregnant women undergoing hysterectomy and 51 pregnant women undergoing caesarean section, of whom there were 39 normotensive and 12 with pre‐eclampsia. Methods Resistance arteries, dissected from myometrial biopsies, were mounted on a wire myograph and preconstricted with vasopressin then subjected to incremental doses of bradykinin. Results Endothelium‐dependent relaxation to bradykinin was seen in the vessels of nonpregnant and normotensive pregnant women. Markedly reduced endothelium‐dependent relaxation was found in the myometrial arteries from women with pre‐eclampsia when compared with both nonpregnant (P < O.000l) and normotensive pregnant (P < 0.0001) women. Conclusion A significant loss of endothelium‐dependent relaxation in myometrial resistance arteries in pre‐eclampsia may contribute to the altered vasoreactivity seen in pre‐eclampsia, and particularly to the decreased placental perfusion and fetal growth retardation commonly associated with this condition.