Immunolocalization and expression of prohibitin, a mitochondrial associated protein within the rat ovaries

This study was designed to determine the cellular distribution and pattern of expression for the mitochondria-associated, protein, prohibitin, during the transitional stages of follicular differentiation within the rat ovary. Immunohistochemical staining techniques were used on frozen sections to ex amine the localization of prohibitin to preantral, antral, preovulatory, an d atretic follicles. Prohibitin localization was also determined in corpus luteum from adult rats, in addition to those from infant and juvenile ovari es, before and after gonadotropin stimulation. Western and Northern blottin g techniques were used for qualitative and quantitative assessment of prohi bitin expression levels within the ovary. Prohibitin was localized within g ranulosa cells of infant and juvenile ovaries in a relatively heterogeneous staining pattern. The oocyte also exhibited robust prohibitin expression a t all stages of follicular development. In addition, strong prohibitin expr ession was evident in the corpus luteum as well as in follicles undergoing atresia. Additional data derived from studies involving a GnRH-agonist indi cate that increases in prohibitin protein expression correlate with the ini tial events of apoptosis. Collectively, these results support a growth regu latory role for prohibitin within the rat ovary. Therefore, we propose that prohibitin may serve as an important regulator of granulosa cell fate duri ng follicular development. Anat Rec 256:40-48, 1999. (C) 1999 Wiley-Liss, I nc.