Yield, characteristics, motility and cAMP content of sperm isolated from seven regions of ram epididymis.

Abstract

Highly pure suspensions of intact, viable sperm were obtained from each of seven regions of the ram epididymis after eliminating virtually all erythrocytes by perfusing the vascular system with saline. Sperm were liberated into buffer by slicing the tissue and the resulting suspension was passed through a 37-µm mesh nylon filter and gently centrifuged. A mean of 7–15 × 108 cells was obtained from the central caput, distal caput, proximal corpus and distal corpus. Of all cells in these suspensions, 80–92% were intact sperm as judged by light and scanning electron microscopy. For the proximal and distal cauda, suspensions contained 80–88 × 108 cells of which >97% were intact sperm. Changes in sperm associated with their maturation were analyzed using these suspensions. For samples suspended in buffer (including glucose), ≤3% of the sperm from the central caput or proximal corpus were progressively motile as contrasted to 41% of the sperm from the proximal cauda. Addition of partially purified forward motility protein plus caffeine to the buffer increased the percentage of motile sperm in samples from the proximal corpus, but not the central caput or proximal cauda epididymidis. The cAMP content of sperm from the caput or corpus epididymidis was low (5–6 pmoles/lO8 cells) after 1 h of incubation. Sperm from the proximal cauda did not contain significantly more cAMP than those from the proximal corpus, but sperm from the distal cauda contained significantly more cAMP (approx. 13 pmoles/108 cells) than sperm from any other region. Sperm from both the proximal and distal cauda epididymidis were motile and no simple relationship between cAMP content and sperm motility was discerned. However, estimated cAMP concentrations for the motile and immotile subpopulations are consistent with the concept that a threshold level of cAMP is required for the initiation of motility.