Development and initiation of sperm motility in the hamster epididymis

Hamster spermatozoa were isolated from the caput, corpus and cauda epididymidis. They were observed in culture medium at 37 degrees C with a phase-contrast microscope and their motility recorded cinematographically. About 20 p. 100 of the caput epididymidis spermatozoa were motile and moved in a confined space with no forward progression. 30 p. 100 of the corpus epididymidis spermatozoa were motile, showing increased flagellar activity and moving in wide circles. 90 p. 100 of the cauda epididymidis spermatozoa were motile and moved forward. Forward motility was induced in immotile spermatozoa from the caput epididymidis by adding cyclic 3'-5' adenosine monophosphate (cAMP) phosphodiesterase inhibitors (caffeine, theophylline, IMX) and epididymal plasma. The best stimulation was initiated by 15 mM caffeine with 10 p. 100 of cauda epididymal plasma; a mean of 60 p, 100 of forward motility was obtained which lasted for one hour and then ceased. Cinematographic studies revealed that some induced sperm movements differed from the equivalent natural ones by the amplitude of the head movements. It is shown that during epididymal transit of hamster spermatozoa, the induction of forward motility requires not only an increased cAMP level but also factors from the cauda epididymal plasma. The idea that glycoprotein of epididymal origin initiates forward motility is discussed.