The plasma membrane Ca-ATPase protein from red blood cells is not modified in preeclampsia

Plasma membrane Ca-ATPase activity diminishes by about 50% in red blood cells during preeclampsia. We investigated whether the number of Ca-ATPase molecules is modified in red cell membranes from preeclamptic pregnant women by measuring the specific phosphorylated intermediate of this enzyme. Also, we isolated the Ca-ATPase protein from both normotensive and preeclamptic pregnant women and estimated its molecular weight, and its cross-reactions with specific polyclonal and monoclonal (5F10) antibodies against it. We measured the Ca-ATPase activity in a purified state and the effect of known modulators of this ATPase. It was found that the phosphorylated intermediate associated with PMCA is similar for red cell ghosts from normotensive and preeclamptic women, suggesting a similar number of ATPase molecules in these membranes. The molecular weight of the Ca-ATPase is around 140 kDa for both normotensive and preeclamptic membranes, and its crossreactions with specific antibodies is similar, suggesting that the protein structure remains intact in preeclampsia. Calmodulin, ethanol, or both calmodulin plus ethanol, stimulated the Ca-ATPase activity to the same extent for both normotensive and preeclamptic preparations. Our results showed that the reduced Ca-ATPase activity of the red cell membranes from preeclamptic women is not associated with a defective enzyme, but rather with a high level of lipid peroxidation. © 2005 Elsevier B.V. All rights reserved.