Steroid concentrations and immunoexpression of steroidogenic enzymes in ovaries of aged bank voles: effect of photoperiod.

The main objective of the present study was to establish morphological and steroidogenic changes occurring in the ovaries of senescent bank voles, with respect to the photoperiod of rearing. Obtained results revealed less pronounced changes in the ovaries of females reared in a long photoperiod (LD). Their gonads still possessed some healthy follicles and old corpora lutea (CLs). Senescence-related changes encompassed the presence of abnormal follicles, large regions containing extra-follicular luteinized granulosa cells and numerous clusters of hypertrophied theca/interstitial cells, exhibiting strong expression of 3β-hydroxysteroid dehydrogenase (3β-HSD) and much weaker that of cytochrome P450c17. More pronounced changes were observed in animals reared in short day (SD) conditions and included the presence of only few, usually abnormal follicles and/or remnants of CLs in the surface region, and the isle-like clusters of cells in the ovarian medulla. The clusters were composed of cells generally featuring strong 3β-HSD and/or P450c17 immunoreaction. Steroid content analysis revealed that progesterone dominated in the ovaries of LD bank voles and androgens in SD animals, while estradiol content was very low in both investigated groups. These studies showed for the first time morphological and steroidogenic changes found in the ovaries of senescent bank voles and indicated an important role of length light conditions in the process of reproductive aging.