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

1α,25-Dihydroxyvitamin D(3) (1,25D(3)) 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 1,25D(3) 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 1,25D(3). The results demonstrated that 1,25D(3) 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 Ca(2+)-dependent K(+) channels and Ca(2+)-dependent Cl(-) channels, are involved in the mechanism of action. The use of BAPTA-AM showed that [Ca(2+)](i) was also implicated, and the incubation with digoxin produced an increase in (45)Ca(2+) uptake indicating that the effect of 1,25D(3) may also result from Na(+)/K(+)-ATPase inhibition. In addition, 1,25D(3) was able to increase the GGTP activity. Considered together, our results indicate a PKA/PKC/MEK-dependent 1,25D(3) pathway as well as ionic involvement leading to (45)Ca(2+) uptake in immature rat testis. These findings demonstrate that 1,25D(3) stimulates calcium uptake and increases GGTP activity which may be involved in male reproductive functions.