Regulation of aromatase expression by 1α,25(OH)2 vitamin D3 in rat testicular cells.

It is well known that the vitamin D endocrine system is involved in physiological and biochemical events in numerous tissues, especially gut, bone and kidney but also testis. Therefore, in this study the effect and mechanisms of action of 1α,25(OH)(2) vitamin D(3) (1,25D) on aromatase gene expression in immature rat Sertoli cells were evaluated. Vitamin D receptor transcripts were present in immature Sertoli cells as well as in adult testicular germ cells and somatic cells. The treatment of immature Sertoli cells with 100 nM 1,25D increased the amount of aromatase transcript, mainly in 30-day-old rats. The protein kinase A (PKA) blocker, H89, partially inhibited the 1,25D effect. The stimulation of aromatase gene expression in 30-day-old Sertoli cells by the agonist 1α,25(OH)(2) lumisterol(3), and the suppression of the 1,25D effect by the antagonists 1β,25(OH)(2) vitamin D(3) and (23S)-25-dehydro-1α (OH)-vitamin D(3)-26,23-lactone suggested, besides a genomic effect of 1,25D, the existence of non-genomic activation of the membrane-bound vitamin D receptor involving the PKA pathway.