Cell-Specific Expression and Regulation of Soluble Guanylyl Cyclase (alpha)1 and (beta)1 Subunits in the Rat Ovary

Soluble guanylyl cyclase (sGC) is activated by nitric oxide (NO) and carbon monoxide, resulting in cGMP production. Recent studies indicate that NO and cGMP influence ovarian functions. However, little information is available regarding the ovarian expression of sGC. The present study examined sGC (alpha)1 and (beta)1 subunit protein levels in the ovary during postnatal development, gonadotropin-induced follicle growth, ovulation, and luteinization as well as in cultured rat granulosa cells. In postnatal rats, sGC (alpha)1 subunit immunoreactivity was high in granulosa cells of primordial and primary follicles on Day 5 but low in granulosa cells of larger follicles on Days 10 and 19. Theca cells of developing follicles, but not stromal cells, also demonstrated moderate sGC (alpha)1 immunoreactivity. In gonadotropin- treated immature rats, intense sGC (alpha)1 subunit staining was similarly observed in granulosa cells of primordial and primary follicles, but such staining was low in granulosa cells of small antral follicles and undetectable in granulosa cells of large antral and preovulatory follicles. Following ovulation, corpora lutea expressed moderate sGC (alpha)1 immunoreactivity. Similar ovarian localization and expression patterns were seen for sGC (beta)1, indicating regulated coexpression of sGC subunits. Immunoblot analysis revealed no change in total ovarian sGC (alpha)1 and (beta)1 subunit protein levels during gonadotropin treatment. Similarly, no effect of FSH on sGC subunit protein levels was apparent in cultured granulosa cells. These findings indicate regulated, cell- specific patterns of sGC expression in the ovary and are consistent with roles for cGMP in modulating ovarian functions.