Fetal expression of GnRH and GnRH receptor genes in rat testis and ovary

Abstract

The identification of gonadal gonadotropin-releasing hormone receptors (GnRH-R) and evidence of direct inhibitory effects of GnRH agonists upon steroidogenesis in adult rat gonads, lend credence to a putative intragonadal role of a locally secreted GnRH or GnRH-like peptide. Using reverse transcription-polymerase chain reaction followed by Southern blot hybridization and sequencing, we identified, both in the ovary and in the testis of fetal and adult rats, a fully processed GnRH messenger RNA (mRNA), the sequence of which, in adult testis, was identical to that found in the hypothalamus. We also detected in the testis, but not in the ovary, a transcript containing the first intron.The ontogeny of GnRH and GnRH-R gene expression was studied in rat gonads from 14·5 to 21·5 days postcoitum (dpc), using dot blot hybridization of total RNA. During this period, the levels of cyclophilin mRNA normalized to total RNA remained unchanged. Thus, we used cyclophilin as an internal standard. GnRH mRNA was detected in the ovary at 18·5 dpc, four days later than in the testis, and similar levels were found in both sexes at birth. GnRH-R mRNA was present at 14·5 dpc in the testis and at 15·5 dpc in the ovary, with the levels at 21·5 dpc being 2·4 times higher in the testis than in the ovary. GnRH and GnRH-R mRNA levels increased in both sexes in late fetal development, but this increase appeared two days sooner in the ovary compared with the testis, thus supporting the hypothesis that expression of the GnRH and GnRH-R genes is regulated in a sexdependent manner during fetal development. In all cases, expression of GnRH and GnRH-R preceded gonadotropin receptors in the gonads and initiation of gonadotropin secretion by the pituitary.

Rat Gnrhr promoter directs species-specific gene expression in the pituitary and testes of transgenic mice

“…To date, based on functional and morphological criteria, it is believed that these two cell populations represent two distinct lineages (O'Shaughnessy et al 2006). Using RT-PCR approaches in rat foetal gonads, we have previously identified Gnrh and Gnrhr transcripts as soon as 14.5 dpc (Botte et al 1998). Interestingly, the foetal expression pattern of Gnrhr in the testis displayed an acute rise at late gestation starting at 20.5 dpc that corresponds to the onset of testis responsiveness to GnRH (Habert et al 1991, Habert 1992).…”

Immunoreactivity for Gonadotropin-Releasing Hormone in Microdialyzed Perfusates of Bovine Mature Follicles In Vitro.

“…The source of GnRH-IR and its molecular characteristics should be clarified in further studies. GnRH-like protein, GnRH mRNA, specific highaffinity binding sites for GnRH, and GnRH receptor mRNA have been demonstrated to be present in rat ovarian tissues [1,[6][7][8][9][10][11]. A previous study reported that the expression of GnRH receptor mRNA in the rat ovary varies during the reproductive cycle.…”

“…The presence of GnRH-like protein, GnRH mRNA, specific high-affinity binding sites for GnRH, and GnRH receptor mRNA have been demonstrated in the rat ovary [1,[6][7][8][9][10][11]. The bovine granulosa cells also contain higher concentrations of GnRH-like protein than other ovarian and extraovarian tissues [12].…”

Gonadotropin-releasing hormone and its receptor in normal and malignant cells

“…In the testes, GnRH mRNA is expressed in Sertoli cells while the GnRHR is expressed in the Leydig cells by RT-PCR (Bahk et al 1995, Botte et al 1998. In early fetal development in the rat, GnRH mRNA expression in the testis precedes that in the ovary, followed by GnRHR expression.…”