Role of 1α,25(OH) 2 vitamin D 3 on α-[1- 14C]MeAIB accumulation in immature rat testis

Abstract

1,25D 3 is critical for the maintenance of normal reproduction since reduced fertility is observed in male rats on a vitamin D-deficient diet. Vitamin D-deficient male rats have incomplete spermatogenesis and degenerative testicular changes. In the present study we have examined the ionic involvement and intracellular messengers of the stimulatory effect of 1,25D 3 on amino acid accumulation in immature rat testis. 1,25D 3 stimulates amino acid accumulation from 10 −12 to 10 −6 M by increasing the slope to reach a maximum value at 10 −10 M, as compared to the control group. No effect was observed at a lower dose (10 −13 M). Time-course showed an increase on amino acid accumulation after 15, 30, and 60 min of incubation with 1,25D 3 (10 −10 M). 1,25D 3 stimulated amino acid accumulation in 11-day-old rat testis but not in testis that were 20 days old. Cycloheximide totally blocked the 1,25D 3 action on amino acid accumulation. Furthermore, a localized elevation of cAMP increased the stimulatory effect of 1,25D 3 and the blockage of PKA nullified the action of the hormone. In addition, 1,25D 3 action on amino acid accumulation was also mediated by ionic pathways, since verapamil and apamine diminished the hormone effect. The stimulatory effect of 1,25D 3 on amino acid accumulation is age-dependent and specific to this steroidal hormone since testosterone was not able to change amino acid accumulation in both ages studied. This study provides evidence for a dual effect for 1,25D 3, pointing to a genomic effect that can be triggered by PKA, as well as to a rapid response involving Ca 2+/K + channels on the plasma membrane.