EFFECTS OF OUABAIN ON THE ISOLATED HUMAN UTEROPLACENTAL VASCULATURE

OBJECTIVE: We sought to describe the effects of ouabain on the human u teroplacental vasculature. STUDY DESIGN: Stem villous vessels and intr amyometrial arteries isolated from placental and myometrial biopsy spe cimens at term were mounted in organ baths. Moreover, isolated human p lacental cotyledons were perfused. RESULTS: Contractions induced by th e thromboxane A(2) 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 wi th ouabain 10(-7) to 10(-6) mol/L. These associations were unaffected by removal of the endothelium. In maternal arteries ouabain (10(-6) mo l/L) failed to significantly affect nitric oxide-induced relaxation. O uabain (10(-9) mol/L) significantly affected pressure-flow relationshi ps in perfused cotyledons. CONCLUSIONS: Ouabain impairs nitric oxide-i nduced 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 uterop lacental blood flow.