CORTICOTROPIN-RELEASING HORMONE (CRH) IS EXPRESSED AT THE IMPLANTATION SITES OF EARLY PREGNANT RAT UTERUS

We have shown previously that the epithelial cells of human endometriu m produce CRH. The biological role of endometrial CRH is not yet known . Among other things, CRH appears to be involved in the inflammatory p rocess, acting as an autocrine/paracrine proinflammatory regulator. Si nce the reaction of endometrium to the invading blastocyst has charact eristics of an aseptic inflammatory reaction, we have hypothesized tha t endometrial CRH may participate in the inflammatory phenomena taking place at the implantation site of blastocyst. In the present study we demonstrate a higher content of immunoreactive (IR)-CRH and CRH mRNA in the implantation sites of early pregnant rat uterus compared to the inter-implantation regions. Specifically we have found that : a) rat uterus contained a 1.3 kb CRH transcript, similar or identical in size to that present in human placenta, b) the size of the IR-CRH present in uterine extracts was similar to authentic hypothalamic CRH, c) Nort hern blot analysis showed that the content of CRH mRNA in uterus at th e implantation sites was 3.5 fold higher compared to that in the inter -implantation regions and finally, d) immunohistochemical localization of IR-CRH in early pregnant rat uterus revealed positive staining of the luminal epithelial cells in both implantation and inter-implantati on uterine regions, while decidualized stromal cells were positive onl y at the implantation sites. Our data suggest that endometrial CRH may play a role in the implantation of blastocyst.