Immunohistochemical detection of atrial natriuretic factor (ANF) in different ovarian cell types

Atrial natriuretic factor (ANF) and its receptors were identified in various tissues and organs including the female reproductive system. The present studies were undertaken to investigate ANF localization in immature rat ovaries, and the changes of ANF expression in response to different ovarian hormonal conditions.

ANF was characterized immunocytochemically during different ovarian status using an animal model with synchronized ovarian follicular growth and atresia induced by pregnant mare serum gonadotropin (PMSG). This treatment in prepubescent rats produces a series of ovarian changes mimicking follicular growth and differentiation (48 h after PMSG treatment) and atresia (96 h after PMSG treatment) and permits the synchronization of events for investigation purposes.

Our findings showed that in immature rat ovaries ANF was localized primarily in granulosa cells of all developing follicles (healthy and atretic). Immunocytochemical analysis revealed that during follicular growth and differentiation (48 h after PMSG) ANF was present in all steroid producing cells - interstitial, thecal and granulosa cells. ANF immunoreactivity was also detected in the cytoplasm and nuclear compartment of the growing oocytes. In all atretic follicles ANF staining was detected at 96 h after PMSG injection, but the intensity of the reaction varied with the degree of atresia, the mostly pronounced reaction being observed in the late stage of atresia.

These results indicate that ANF represents a unique peptide, which is expressed in different ovarian cell types and responds to different developmental programming.