IN-SITU DETECTION OF GONADOTROPIN-RELEASING-HORMONE (GNRH) RECEPTOR MESSENGER-RNA EXPRESSION IN THE RAT OVARIAN FOLLICLES

To clarify the target cells of GnRH in the ovary, in vivo expression o f ovarian GnRH receptor mRNA was examined histologically by in situ hy bridization in immature rats treated with PMSG only or in combination with hCG. Strong hybridization signals were observed in the granulosa cells of atretic follicles. However, no significant signals were found in the granulosa cells of healthy small, preantral, or early antral f ollicles. Healthy Graafian and preovulatory follicles also showed inte nse signals in their mural granulosa cells, but no signals were detect ed in the cumulus oophorus cells. Corpora lutea showed only weak signa ls, but luteinizing follicles probably after atresia exhibited signals of moderate intensity in their luteinized and remaining granulosa cel ls. No signals were detected in the theca cells and oocytes in all the follicles. Interstitial cells sometimes exhibited hybridization signa ls of moderate intensity, when the cells were eosinophilic. Pretreatme nt with different combinations of gonadotropins yielded different ovar ian histology, but this had no influence on the localization of hybrid ization signals. These results, showing that the authentic GnRH recept or mRNA was expressed in a certain cell population in the rat ovary, s uggest that the receptor is involved in the control of various ovarian functions including follicular development, atresia, ovulation, and l uteinization after ovulation and follicular atresia. (C) 1995 Wiley-Li ss, Inc.