Distinct regulation by steroids of messenger RNAs for FSHR and CYP19A1 in bovine granulosa cells

Steroidal regulation of gene expression in follicular cells is not completely defined. Granulosa cells from 5 mm bovine follicles were cultured and treated and steady-state mRNA levels determined for FSHR (follicle-stimulating hormone receptor) and CYP19A1 (aromatase). Cells were treated for 5 days with (0.1-300 ng/ml) 17beta-estradiol (E), testosterone (T), or 5alpha-dihydrotestosterone (DHT). FSHR mRNA was increased by T and DHT but not E-2. In contrast, CYP19A1 mRNA was induced by all doses of E 2 but only high doses of T and DHT. Similarly, varying treatment duration (1-5 days) showed that FSHR was increased by T and DHT and CYP19A1 mRNA increased by E 2 and T at all times. Synergism between steroid hormones and FSH or forskolin was also evaluated. FSH or E-2 did not alter FSHR mRNA and did not enhance DHT stimulation of FSHR mRNA. In contrast, DHT alone had no effect on CYP19A1 mRNA but synergized with FSH plus E-2 to increase CYP19A1 mRNA, probably due to induction of FSHR by DHT. Effects of E-2 and T on CYP19A1 were blocked by ICI 182,780, indicating mediation by estrogen receptors. However, the specific androgen receptor antagonist bicalutamide did not block E 2 or T effects on CYP19A1 but did block T and DHT stimulation of FSHR. Thus, FSHR is specifically regulated through androgen receptor, whereas CYP19A1 is regulated by multiple pathways, including estrogen receptors and cAMP/protein kinase A induced by FSHR activation in granulosa cells. These inter and intracellular regulatory mechanisms may be critical for normal follicle growth and dominant follicle selection.