Regulation of low density lipoprotein receptor mRNA levels by estradiol 17beta and chorionic gonadotropin in human placenta.

Inhibition of synthesis of estradiol 17beta by the addition of inhibitors of aromatase, a key enzyme in the biosynthesis of estradiol 17beta, or addition of tamoxifen - an estrogen receptor antagonist, to human placental minces resulted in an increase in the level of LDL-receptor mRNA. This increase could be blocked by the simultaneous addition of estradiol 17beta. A concentration dependent effect of estradiol 17beta on the level of LDL-receptor mRNA was seen both in first trimester, and term placenta. Addition of human chorionic gonadotropin (hCG) to term placental minces also increased the LDL-receptor mRNA levels. When hCG and cycloheximide were added together, an additive effect was observed. The results obtained in this study suggest that the LDL-receptor mRNA levels in the human placenta are regulated by estradiol 17beta and hCG.