Regulation of epididymal function and sperm maturation--endocrine approach to fertility control in male.

The structural and functional integrity of the epididymis, the acquisition of fertilizing ability by spermatozoa and their viability within the epididymis are androgen dependent phenomena. Although the precise mechanism by which sperm maturation and viability in the epididymis are brought about by androgen are not clearly understood, it is generally held that specific epididymal secretions produced under the influence of androgen affect these events. Though the spermatozoa appear to remain viable in a low androgen environment, sperm maturation requires a relatively high androgen environment. Against this background the potentiality of antiandrogens as extragonadal antifertility agents has been discussed. Studies with steroidal and nonsteroidal antiandrogens have revealed that in adult animals the secretory activity of the epididymis, as evidenced by the level of glycerylphosphorylcholine, either remains unaffected or is stimulated under their influence. These studies have further indicated that the extragonadal antifertility action of antiandrogens will depend upon their ability to (1) lower the testicular androgen synthesis and/or androgen binding protein, which possibly serves as a carrier of androgen from the testis to epididymis; (2) to lower local androgen synthesis as a result of reduced levels of circulating androgen, and (3) to inhibit 5 alpha-reduction of testosterone to dihydrotestosterone and/or to inhibit androgen binding to receptors. Success in the rational development of new antifertility agents for male which will act by controlling epididymal function will depend upon a clear understanding of the factors that regulate epididymal secretion and the role of epididymal secretions in sperm maturation and survival.