Localization of angiotensin-(1-7) and Mas receptor in the rat ovary throughout the estrous cycle

We have previously demonstrated the presence of Angiotensin (Ang)-(1-7) in rat ovary homogenates and its stimulatory effect on estradiol and progesterone production. The present study was undertaken to identify the cellular localization of Ang-(1-7) and its receptor Mas in the rat ovary in the different phases of the estrous cycle. Ang-(1-7) and Mas were localized by immunohistochemistry and Mas mRNA expression was assessed by RT-PCR. Immunostaining for both Ang-(1-7) and Mas was found in all phases of the estrous cycle, particularly in the thecal and interstitial cells, as well as in regressing corpora lutea. However, granulosa cells were positive only in antral and preovulatory follicles at proestrus and estrus phases. This pattern contrasted with the distribution of the octapeptide Ang II, which was abundant in granulosa but not in theca cells. In addition, the expression of Mas mRNA was demonstrated in all estrous cycle phases. Angiotensin-converting enzyme activity did not vary between estrous cycle phases, whereas prolyl endopeptidase activity was significantly higher in diestrus and neutral endopeptidase activity was significantly higher in metestrus. These data provide the first evidence that new RAS components are dynamically expressed in the ovary across the rat estrous cycle. Further functional studies should clarify the role of Ang-(1-7) signaling through Mas receptor in the regulation of ovarian physiology.