[Renin-angiotensin system of the uterus and ovary in mammalian females].

The circulating reninangiotensin system (RAS) participates in the regulation of blood pressure and electrolyte metabolism. Renin, a proteolytic enzyme, synthesized in the kidney from its biological precursor, prorenin, cleaves its substrate angiotensinogen in the blood to form the active octapeptide, angiotensin II (AII). All the RAS components are present in the reproductive system of mammals. During pregnancy, the level of prorenin increases in the plasma. The ovary is the source of this prorenin during early pregnancy and maternal decidua later on. During the menstrual cycle, the thecal of preovulatory follicles synthesize prorenin, renin and AII. Thecal renin synthesis is controlled by LH/hCG as demonstrated in vivo and in vitro in the rabbit. Ovarian renin seems to be identical to kidney renin. Prorenin appears to be the major secretory product rather than renin, which remains intracellular. AT2-type angiotensin II-receptors are expressed in the rat on follicular granulosa cells and could be down-regulated by FSH. The bovine thecal cells also express AT2-receptors, up-regulated by LH. These data are consistent with an autrocrine or paracrine role for ovarian RAS. It has been implicated in neovascularization of the follicle and regulation of steroidogenesis by increasing the androgen/estrogen ratio, an index of follicular atresia.