Chorion laeve trophoblasts of preeclamptic fetal membranes: histochemically detectable enzyme activities do not change at a subcellular level

We examined the subcellular localization of ADP-degrading activity and cyto chrome c: oxidase (CCO) activity in chorion laeve trophoblasts from term an d near term human fetal membranes, and compared them with those from severe preeclamptic fetal membranes. The methods used for the detection of enzyme activities were the lead nitrate method for ADP-degrading activity and the diaminobenzidine method for CCO. Precipitates indicative of ADP-degrading activity were visible on surface microvillous plasma membranes of chorion l aeve trophoblasts both from normal and preeclamptic fetal membranes. The in tensity and distribution patterns were the same in the normal and preeclamp tic subjects. CCO labeling was visible in almost all laeve trophoblastic mi tochondria both in normal and preeclamptic cases. Previously, we demonstrat ed that in preeclamptic villous trophoblasts there were decreases in ADP-de grading activity and the presence of CCO-negative mitochondria, which were proposed to lead to dysfunction of each villous trophoblast, and finally to placental insufficiency in preeclampsia. Reductions or changes in enzyme i ntensities/distribution patterns, which are characteristic features of pree clamptic villous trophoblasts, were absent in chorion laeve trophoblasts in preeclampsia. These results suggest that in preeclampsia there are no, or at least less severe, abnormalities in the enzyme activities of chorion lae ve trophoblasts, compared with villous trophoblasts, as far as enzyme-histo chemically detectable enzymes are concerned.