Expression of G proteins in human placentas from pregnancies complicated by gestational hypertension.

Preeclampsia (gestational hypertension) is accompanied by decreased hPL and increased hCG levels in maternal serum. The expression of these peptides as well as the endocrine mechanisms responsible for their regulation in preeclampsia are unknown. We have demonstrated that regulatory GTP-binding proteins (G proteins) are implicated in the modulation of hPL production by placentas from normal pregnancies. In order to extend our knowledge on placental endocrinology, we analyzed in this study the expression of hPL and beta-hCG mRNAs as well as placental G protein alpha-subunits in pregnancies complicated by gestational hypertension. Western and Northern blot analyses were respectively performed on membrane protein and total mRNA preparations from human placentas of preeclamptic (n = 7) and normal pregnancies (n = 4). The levels of hPL and beta-hCG mRNAs were respectively 108% and 105% of those from normal placentas, suggesting that the altered circulating levels of hPL and beta-hCG are not related to dysfunctional mRNA expression of these peptides. The autoradiographs for G proteins and their mRNAs showed no difference in G protein expression between preeclamptic and normal tissues. Specifically, G alpha i2, G alpha i3, G alpha o, G alpha s, and G alpha q/11 levels reached 87%, 81%, 91%, 99%, and 103% respectively of those from normal placentas. In parallel with the protein levels, their mRNAs expression were respectively 93%, 89%, 113%, 104%, and 94% of normal values for G alpha i2, G alpha i3, G alpha o, G alpha s, and G alpha q/11. These results suggest that neither a change in hPL and beta-hCG expression nor a change in signal transduction machinery is implicated in the altered circulating levels of hPL and beta-hCG in preeclampsia.