Expression of angiotensinogen in the uterus induced by coagulating gland renin in mice

Coagulating gland (CG) renin is one of the components of the local renin-angiotensin system (RAS), which plays important roles in the maintenance of homeostasis in several tissues. Although the existence of local renin has been reported in many tissues, its function is not yet well understood. In the present study, the relationship between CG renin and uterine angiotensinogen was investigated by immunohistochemical and in situ hybridization techniques. In mating experiments with male and female C57BL/6 mice, renin was demonstrated immunohistochemically on the epithelial cells of the uterus on the first day after coitus; however, it was not detected on the second and third days after coitus. Neither immunoreactive cells nor messenger signals for renin were demonstrated on the epithelial cells of the uterus throughout the experiments. On the first day after mating, it was noted that positive signals for angiotensinogen mRNA were expressed on the epithelial cells of the uterus in situ hybridization, but not on the second and third days after coitus. These results suggest the possibility that CG renin is transferred to the uterine epithelium at mating and temporarily activates the expression of angiotensinogen in the uterus. Angiotensin II produced by angiotensinogen may act as an important mediator for vascularization of the first step of pregnancy.