Functional Importance of 1α,25(OH)2-Vitamin D3and the Identification of Its Nongenomic and Genomic Signaling Pathways in the Testis

The 1α,25(OH)2-vitamin D3(1,25-D3) is known by its classic effects on Ca2+metabolism and regulation of cellular proliferation and differentiation. The hormone 1,25-D3acts in the testis through nongenomic and genomic events being implicated in the success of spermatogenesis in rats and in human being. The aim of this review was to highlight the effect and intracellular pathways of 1,25-D3to modulate the spermatogenesis. The pivotal role of 1,25-D3in male reproduction is reinforced by the presence of VDR and 1α-hydroxylase in reproductive tract. Also, the marked expression of VDR and the VD metabolizing enzymes in human testis, ejaculatory tract, and mature spermatozoa implicates the 1,25-D3in spermatogenesis and maturation of human spermatozoa. Among genomic events, 1,25-D3influences the expression of calcium binding protein and stimulates aromatase gene expression through a nongenomic activation of the membrane-bound VDR receptor involving the PKA pathway in the testis. Also, 1,25-D3stimulates amino acid transport and exocytosis in testis by nongenomic events coupled to ionic currents triggered at plasma membrane. All together, the demonstration that 1,25-D3regulates both Sertoli cell and sperm function may be useful for the study and development of new therapeutic strategies for the male reproductive disorders.