Effects of Rete Testis and Epididymal Fluid on the Metabolism and Motility of Testicular and Post-Testicular Spermatozoa of the Ram

The interaction between fluids and spermatozoa from the rete testis and cauda epididymidis have been studied. Both rete testis fluid (RTF) and cauda epididymal fluid (CEF) stimulated the oxygen uptake of epididymal or ejaculated spermatozoa more than that of testicular spermatozoa. Substituting ejaculated for epididymal spermatozoa did not affect the results for “post-testicular” spermatozoa. Concentrated RTF obtained by ultrafiltration (MW cut off = 10,000) was more effective than RTF filtrate in stimulating the respiration and/or motility of the spermatozoa. The addition of glucose had a masking effect on the stimulation by reproductive tract fluids of the respiratory activity and motility of the spermatozoa. However, concentrated RTF and RTF filtrate enhanced glycolysis of epididymal or ejaculated spermatozoa, whereas CEF had a sparing effect on the utilization of glucose by testicular and post-testicular spermatozoa. Each of the fluids depressed the oxidative metabolism of glucose by the spermatozoa. Concentrated RTF increased the rate of glucose degradation to lactic acid in both testicular and post-testicular spermatozoa. The lactic acid metabolism of epididymal and ejaculated spermatozoa in the absence of glucose suggests that the naturally occurring organic acid may at least partially account for the stimulating effect of the fluid on spermatozoal respiration and motility.