Gene expression of gonadotropin-releasing hormone in early pregnant rat and steroid hormone exposed mouse uteri.

While gonadotropin-releasing hormone (GnRH) or GnRH-like substance have been reported to exist in nonhypothalamic tissues such as placenta, gonads, and mammary gland, there have been no reports concerning the detection of GnRH mRNA in uterine tissue. In order to investigate the presence of GnRH in decidual tissues and its possible involvement in the regulation of placental function, we examined the gene for GnRH in the rodent uterus in early pregnancy and in nonpregnant animals treated with female sex steroids. Using RT-PCR and in situ hybridization we found GnRH mRNA transcripts in the rat uterus of 3rd and 6th day gestation and in the mouse uterus treated with estrogen and progesterone. In situ hybridization revealed that GnRH mRNA was localized in the endometrial stromal cells of the 3rd and 6th day of gestation. These results suggest the existence of GnRH gene expression in uterine stromal cells and its possible paracrine effect derived from the decidual cells.