EXPRESSION OF PROSTACYCLIN AND THROMBOXANE SYNTHASES IN PLACENTA AND PLACENTAL BED AFTER PREECLAMPTIC PREGNANCIES

Prostacyclin and thromboxane are potent antagonistic regulators of vas cular tone and platelet aggregation. In pre-eclampsia, the ratio of th eir metabolites is decreased. Little is known about the local regulati on of intrauterine prostacyclin and thromboxane production in this con dition. Placenta and placental bed biopsies were obtained from uncompl icated and pre-eclamptic pregnancies. Prostacyclin synthase (PCS) and thromboxane synthase (TXS) and their mRNA's were localized by immunohi stochemistry using monoclonal antibodies and in situ hybridization. Pr otein and mRNA levels were quantified by immunoblot and RNase protecti on assay. PCS-like immunoreactivity was found in endothelial cells and leiomyocytes, whereas fetal and maternal macrophages showed positive staining for TXS. Their mRNA was localized to trophoblast and endothel ium, and TXS mRNA could also be detected in macrophages. Quantitative analysis showed no significant difference in intrauterine protein or m RNA expression after pre-eclampsia. The prostacyclin and thromboxane p roduction seems to be compartmentalized within the uteroplacental unit . The expression of their synthesizing enzymes might be regulated post -transcriptionally. Additional regulation of prostaglandin production could be metabolically or on the substrate level and requires further elucidation. (C) 1996 W.B. Saunders Company Ltd