Immunohistochemical analyses revealed that prohibitin was highly expressed in the cytoplasm and perinuclear region of granulosa cells of some, but not all, preantral follicles. This pattern of prohibitin immunostaining appeared to be inversely related to that of PCNA expression and remained consistent during subsequent stages of follicular growth. This apparent heterogeneous expression pattern of prohibitin may be indicative of a diverse population of growing cells.
These observations support the notion that prohibitin may be a negative regulator of cell growth and, possibly, could exert antiproliferative activity. Based on these observations, prohibitin expression patterns likely correlated with those of P450scc in granulosa cells as the follicles matured, suggesting that prohibitin may mediate establishment of the steroidogenic machinery of the follicle during development. In support of this contention is the observation that, at the preantral stage of follicular development, prohibitin expression in the theca-interstitial cells was low or undetectable and that these cells were devoid of P450scc.