The ontogeny of components of the renin–angiotensin system in the porcine fetal ovary

There is an autonomous renin–angiotensin system (RAS) in the adult ovary. Renin is present in the primitive kidney, and the fetal ovary develops from the nephrogenic ridge. We hypothesised that components of the ovarian RAS would be present from early gestation, with potential roles in ovarian development. We studied fetal pig ovaries from approximately day 45 (∼0.39 gestation) to term and measured mRNA (RT-PCR) for prorenin, angiotensinogen and the angiotensin II (AngII) Type 1 and 2 receptors (AT1 and AT2), and protein expression (Western blot) and localization (immunohistochemistry) of the AT1 and AT2 receptors. mRNA for prorenin was present in relatively low abundance from at least day 45 and rose to ∼day 75 of gestation, whilst mRNA for angiotensinogen rose steadily. mRNA for the AT1 receptor was present from approximately day 45 and did not alter significantly with increasing gestation but AT2 receptor mRNA was initially high, falling sharply through pregnancy. The AT1 receptor protein abundance fell steadily to term, whereas the AT2 receptor protein did not change during gestation. Both receptors were localised in the surface epithelium and egg nests, the granulosa cells of primordial, primary and secondary follicles, and the oocytes of all except the secondary follicles. Collectively, our results support the hypothesis that there is a functional RAS in the fetal ovary from at least approximately day 45 of gestation until term and that it may have a paracrine role in ovarian growth and development.