Preeclampsia and calcium-ATPase activity of plasma membranes from human myometrium and placental trophoblast

Objective: We determined calcium-activated adenosine triphosphatase (Ca-ATPase) activity and thiobarbituric acid-reactive substances (TBARS) of plasma membranes from myometrium and placental trophoblast of normotensive and preeclamptic pregnant women. Methods: Samples of myometrium were obtained by uterine biopsies taken upon delivery by cesarean section from nulliparous normotensive and preeclamptic pregnant women. Placentas were obtained after full term vaginal delivery from either normotensive or preeclamptic women. Plasma membrane fractions were prepared from both myometrium and placenta and assayed for Ca-ATPase activity and TBARS. Main Outcome Measure(s): We expected to find a higher level of TBARS and, consequently, a lower activity of Ca-ATPase of the plasma membrane fractions obtained from both myometrium and placenta of preeclamptic women. Results: The Ca-ATPase activity of myometrium and placental trophoblast from preeclamptic women was about 50% lower than that from normotensive women, while the TBARS were higher. Conclusions: A reduced Ca-ATPase activity, caused by an increased level of TBARS, may result in an increase in the cytosolic calcium concentration in the vascular smooth muscle cells of preeclamptic women and thus partially explain the high blood pressure developed by these patients.