Effect of photoperiod on the distribution patterns of androgen receptors and steroid hormone concentrations in ovaries of bank voles

Cellular distribution patterns of the androgen receptor in ovaries of female bank voles, born and reared in long (18:6; LD) or short (6:18; SD) photoperiods, have been studied to understand effects of androgens in female gonads. The photoperiod is one of the most important factors in bank voles, which are seasonal breeders, that regulates both morphology and hormonal function of the ovary. Androgen receptors were visualized immunocytochemically, using a specific monoclonal antibody against androgen receptor protein. LD ovaries contained more follicles and showed a different androgen receptor distribution pattern than SD ovaries. In LD ovaries, androgen receptors were strongly expressed in granulosa cells of primordial, primary, and preantral follicles as well as in theca and stromal cells. Positivity was moderate and limited to antral and cumulus regions in large follicles of LD ovaries. In contrast, androgen receptor immunopositivity was intense in the granulosa layer, theca and interstitial cells of large follicles of SD ovaries. A novel observation was the very intense immunostaining of oocyte cytoplasm in primordial and primary unilaminar follicles of LD ovaries. It can be concluded that the androgen receptor is involved in the maturation of oocytes.