Physiology of the epididymis and induction of functional sterility in the male.

The factors regulating the physiology of the epididymis and the induction of functional sterility by alteration of epididymal function are discussed. The threshold requirement of androgens to maintain the structural and functional integrity of the epididymis in the rat, hamster and monkey is much higher than that needed by the accessory glands. Further, the cauda epididymidis has a higher threshold requirement of androgens than the caput epididymidis and may reflect the differences in the availability and metabolism of androgens to these two segments. An inverse relationship exists between the levels of sialic acid (sialoproteins) in the epididymal luminal plasma and that bound to the spermatozoa in the cauda epididymidis. Androgen deprivation and consequent alteration of the secretory activity of the epididymis either by castration or by treatment with antiserum to LH or by the antiandrogen, cyproterone acetate, caused concurrent decrease in the levels of sialic acid in the luminal plasma and in the spermatozoa of the different regions of the epididymis. These changing patterns of sialic acid in the spermatozoa and luminal plasma may be associated with changes in the surface charge of the spermatozoa and the stabilization of the acrosome and its membranes during sperm maturation.