In-vitro initiation of forward motility in testicular spermatozoa

Initiation of forward motility in vitro was investigated in goat and ram spermatozoa obtained from the rete testis. No forward motility was generated in the immotile testicular spermatozoa when they were incubated in a modified Ringer's solution containing theophylline (30 mM) and epididymal plasma (2 mg protein/ml). However, these reagents induced non-progressive flagellar movement in approximately 25% of spermatozoa. Bicarbonate (25 mM) induced forward motility in approximately 16% of the goat/ram testicular spermatozoa. Theophylline was essential for the bicarbonate-mediated activation of sperm motility, but epididymal plasma had no significant effect on this activation process. Theophylline activated progressive motility in testicular spermatozoa in a dose-dependent manner, the maximum effect occurring after incubation for 10 min with 30 mM theophylline. The initiation profile of in-vitro motility of goat/ram spermatozoa from the caput epididymis closely resembled that of testicular spermatozoa except that induction of motility in the caput spermatozoa was dependent both on bicarbonate and epididymal plasma. The data indicate that, unlike caput epididymal spermatozoa, initiation of motility in testicular spermatozoa is not dependent on motility-promoting protein(s) in epididymal plasma.