Luteinizing hormone induces progesterone receptor gene expression in cultured porcine granulosa cells.

We have examined the effect of LH on the regulation of the progesterone receptor (PR) in cultured porcine granulosa cells. In this study we used the RNase protection assay to evaluate the PR mRNA levels with a porcine cDNA clone isolated by the polymerase chain reaction (PCR) method. This clone was regarded as part of the porcine PR cDNA because of its 98.3% and 95.7% homology to the hormone-binding domain of human PR cDNA in amino acid and nucleotide sequences, respectively. Treatment with LH (500 ng/ml) increased porcine PR mRNA to a maximum level of 8.6 +/- 1.1-fold (mean +/- SE) after 3-h exposure. This induction was mimicked by (Bu)2cAMP as well as by FSH and hCG, and the increased PR caused by LH and (Bu)2cAMP occurred in a dose-dependent manner. Basal and LH-induced PR mRNA levels were not affected by progesterone (100 ng/ml), estrogen (100 ng/ml), and RU 486 (10 ng/ml) at 3 h. The mechanism of the increased PR mRNA levels was studied in the presence of actinomycin-D and cycloheximide. While inhibition of RNA synthesis with actinomycin-D blocked LH-induced PR mRNA expression, inhibition of protein synthesis with cycloheximide increased basal and LH-induced PR mRNA levels. These results indicate that the expression of PR mRNA is positively regulated by LH, and this induction does not require ongoing protein synthesis. There may be a cycloheximide-sensitive mechanism that modulates PR mRNA stability. From our results we suspect that progesterone modulates ovarian function through LH-induced PR in granulosa cells.