Rat sperm enzymes during epididymal transit

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Abstract
The activities of cAMP and cGMP phosphodiesterases (EC 3.1.4.1), adenylate cyclase (EC 4.6.1.1) and protein carboxyl-methylase (EC 2.1.1.24) were measured in the particulate and soluble (105,000 g supernatant) fractions of washed spermatozoa isolated from 5 segments of the adult rat epididymis. The activities of both phosphodiesterases decreased during epididymal transit, while adenylate cyclase and protein carboxyl-methylase underwent a progressive increase, the latter showing the most marked alteration. Both cAMP and cGMP phosphodiesterases as well as the adenylate cyclase were all associated primarily with the particulate fraction, and the extent to which these enzymes were associated with the membranes increased as the spermatozoa passed through the epididymis. Sperm protein carboxyl-methylase activity was predominantly soluble in all segments of the epididymis. Adenylate cyclase, cAMP phosphodiesterase and protein carboxy-methylase activities were found predominantly in the sperm tails, while cGMP phosphodiesterase was equally distributed between heads and tails. The acknowledged increase in intracellular cAMP levels which occurs in spermatozoa during epididymal transit may be a consequence of both increased synthesis (adenylate cyclase) and reduced hydrolysis (phosphodiesterase).

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