The effect of vitamin D on expression of TGF β1 in ovary.

The transforming growth factor β (TGF-β) is thought to have important roles in several stages of folliculogenesis. Vitamin D is effective in cell proliferation, differentition and on estrogen biosynthesis. The aim of the present study was to determine the respective role of 1,25-dihydroxyvitamin D3 on expression of TGF-β1 in developing rat ovaries. 24 (one-mounth-old n = 12 and adult n = 12) female Wistar rats were enrolled in this study. All animals were divided into 4 groups. Group I and II that consist of one-month-old (n = 6) and adult rats (n = 6) respectively served as control groups. Intramuscular vitamin D3 ( 0,05 μgr/kg/every other day) was injected for 8 weeks to group III and IV which consist of one-mounth-old and adult rats respectively. After last injection, ovaries of animals were removed and processed for immunohistochemistry assay. No remarkable differences in staining intensity and localization for TGF-β1 were observed in group I and group III. TGF immunostaining was also predominantly found in oocytes. In granulosa cells, TGF-β1 immunoreactivity was negative. TGF-β1 immunostaining were observed both in nuclei and cytoplasm of granulosa cells in group II. But in group IV granulosa cells and oocytes were negative for TGF-β1. We found that vitamin D administration resulted in a decrease in TGF-β1 levels in the adult rats, but, TGF-β1 expression did not significantly decrease in the newborn rats. However, in multiple linear regression analysis, TGF-β1 expressions were independently associated with vitamin D administration. It is observed that Vitamin D attenuated TGF-β1 expression. The results of this study suggest that vitamin D may play role in folliculogenesis via TGF-β1.