Expression of regulator of G-protein signaling protein-2 gene in the rat ovary at the time of ovulation

The ovulatory process in mammals begins when an endogenous surge in LH circ ulates to the ovary and couples with receptors in the plasma membranes of g ranulosa cells in mature ovarian follicles. This study provides evidence th at the ovulatory stimulus includes induction of the gene for regulator of C -protein signaling protein-2 (RGS2). Immature Wistar rats were primed with 10 IU eCG s.c., and 48 h later the 12-h ovulatory process was initiated by 10 IU hCG (a homolog of LH) s.c. Ovarian RNA was extracted at 0, 2, 4, 8, 1 2, and 24 h after injecting the animals with hCG. The RNA extracts were use d for reverse transcription-polymerase chain reaction differential display to detect gene expression in the stimulated ovarian tissue. Two of the ampl ified cDNAs that were upregulated within 2 h after the ovaries had been sti mulated by hCG were homologous to segments of the mouse gene for RGS2. In s itu hybridization indicated that the RGS2 mRNA was expressed in the granulo sa layer of mature follicles. In conclusion, the gene for RGS2, which is kn own to regulate membrane signaling pathways, is transcribed in ovarian foll icles in response to an ovulatory dose of gonadotropin.