VITAMIN-D MODULATES THE EFFECTS OF FOLLICLE-STIMULATING-HORMONE ON SERTOLI-CELL FUNCTION AND TESTICULAR GROWTH IN SIBERIAN HAMSTERS

Sertoli cells from immature (18-20 day old) Siberian hamsters (Phodopu s sungorus) raised in a long photoperiod (LD; 16hL : 8hD) or a short p hotoperiod (SD; 6hL : 18hD) were cultured and exposed to follicle-stim ulating hormone (FSH) and/or vitamin D-3 (D-3) in vitro. D-3 did not s timulate lactate production when added alone, but significantly augmen ted the stimulatory action of FSH on lactate production by Sertoli cel ls from both LD- and SD-exposed hamsters. Hamsters raised in LD or SD were injected daily with D-3 for 10 days starting at 18 days of age. T his treatment resulted in a significant increase in the testicular wei ght of hamsters raised in LD in which circulating FSH levels are high. In contrast, testicular weight was not altered by D-3 treatment in SD hamsters in which circulating levels of FSH are low. We conclude that D-3, probably after hydroxylation to 1,25(OH)(2) vitamin D-3, modulat es the action of FSH on testicular growth and Sertoli cell function.