Fertility and electrolyte composition of the rat cauda epididymal plasma and spermatozoa before and after castration

Attempts have been made to assess the changes in Na⁺ and K⁺ concentrations in the cauda epididymal plasma and spermatozoa, and to correlate these parameters to changes in fertility shortly after castration in the rat. Fertility was markedly decreased 3 days after androgen withdrawal. By contrast, spermatocrit and Na⁺ concentration in spermatozoa were increased on day 2 post-castration. Neither Na⁺ and K⁺ concentrations in the plasma nor K⁺ inside spermatozoa were altered. The results are discussed in terms of a reduction in the epididymal secretion of macromolecules which are responsible for an increase in net Na⁺ influx into sperm cells.