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-an giotensin system (RAS), which plays important roles in the maintenance of h omeostasis in several tissues. Although the existence of local renin has be en reported in many tissues, its function is not yet well understood. In th e present study, the relationship between CG renin and uterine angiotensino gen was investigated by immunohistochemical and in situ hybridization techn iques. In mating experiments with male and female C57BL/6 mice, renin was d emonstrated 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 througho ut the experiments. On the first day after mating, it was noted that positi ve signals for angiotensinogen mRNA were expressed on the epithelial cells of the uterus in in situ hybridization, but not on the second and third day s after coitus. These results suggest the possibility that CG renin is tran sferred to the uterine epithelium at mating and temporarily activates the e xpression of angiotensinogen in the uterus. Angiotensin II produced by angi otensinogen may act as an important mediator for vascularization of the fir st step of pregnancy.