Effects of ouabain on the isolated human uteroplacental vasculature.

Abstract

We sought to describe the effects of ouabain on the human uteroplacental vasculature. Stem villous vessels and intramyometrial arteries isolated from placental and myometrial biopsy specimens at term were mounted in organ baths. Moreover, isolated human placental cotyledons were perfused. Contractions induced by the thromboxane A2 analog U46619 were unaffected by pretreatment with ouabain 10(-10) to 10(-6) mol/L. In fetal vessels nitric oxide (10(-8) to 3 x 10(-5) mol/L) induced relaxation of vascular tonus induced by U46619 and potassium. This relaxation was inhibited by pretreatment with ouabain 10(-7) to 10(-6) mol/L. These associations were unaffected by removal of the endothelium. In maternal arteries ouabain (10(-6) mol/L) failed to significantly affect nitric oxide-induced relaxation. Ouabain (10(-9) mol/L) significantly affected pressure-flow relationships in perfused cotyledons. Ouabain impairs nitric oxide-induced relaxation of human stem villous arteries and veins, which may explain the changes induced by therapeutically relevant concentrations of the drug on pressure-flow relationships in the perfused cotyledon. Thus treatment with cardiac glycosides in pregnancy may impair uteroplacental blood flow.