Effect of 1α,25-dihydroxyvitamin D3 in plasma membrane targets in immature rat testis: Ionic channels and gamma-glutamyl transpeptidase activity

1α,25-Dihydroxyvitamin D3 (1,25D3) is critical for the maintenance of normal reproduction since reduced fertility is observed in vitamin D-deficient male rats. The aim of this study was to investigate the effect of 1,25D3 in 30-day-old rat testicular plasma membrane targets (calcium uptake and gamma-glutamyl transpeptidase (GGTP) activity), as well as to highlight the role of protein kinases in the mechanism of action of 1,25D3. The results demonstrated that 1,25D3 induced a fast increase in calcium uptake in rat testis through a nongenomic mechanism of action. This effect was dependent on PKA, PKC and MEK. Moreover, ionic channels, such as ATP- and Ca2+-dependent K+ channels and Ca2+-dependent Cl− channels, are involved in the mechanism of action. The use of BAPTA-AM showed that [Ca2+]i was also implicated, and the incubation with digoxin produced an increase in 45Ca2+ uptake indicating that the effect of 1,25D3 may also result from Na+/K+-ATPase inhibition. In addition, 1,25D3 was able to increase the GGTP activity. Considered together, our results indicate a PKA/PKC/MEK-dependent 1,25D3 pathway as well as ionic involvement leading to 45Ca2+ uptake in immature rat testis. These findings demonstrate that 1,25D3 stimulates calcium uptake and increases GGTP activity which may be involved in male reproductive functions.