Immunohistochemical detection and distribution of the 1,25-dihydroxyvitamin D₃ receptor in rat reproductive tissues

Vitamin D₃, via its active metabolite 1,25-dihydroxyvitamin D₃, plays a critical part in male and female reproduction in the rat. 1,25-Dihydroxyvitamin D₃ activity is mediated by an intracellular receptor (VDR). VDR distribution in reproductive tissue has not been studied using antibodies against the receptor. We developed a polyclonal antibody against the VDR and used it to examine VDR distribution in male and female rat reproductive tissues. In rat testes, VDR epitopes were observed in seminiferous tubules, specifically in spermatogonia, Sertoli cells and spermatocytes. Spermatozoa stained faintly. Epithelial cells of the epididymis, seminal vesicles and prostate also expressed VDR epitopes. In the female rat reproductive tract, immunostaining for VDR was seen in ovarian follicles, specifically in granulosa cells. Weaker VDR immunostaining was observed in follicular thecal cells and in the ovarian stroma and germinal epithelium. Corpus luteal cells stained intensely for VDR. Epithelium of fallopian tubes and the uterus also contained VDR epitopes. Both nuclear and cytoplasmic VDR immunostaining was observed in male and female rat reproductive tissues. We conclude that the VDR is widely distributed in male and female reproductive tissues and that it is likely to mediate actions of 1,25-dihydroxyvitamin D₃ in the tissues.