Partial characterization of human spermatozoal phosphodiesterase and adenylate cyclase and the effect of steroids on their activities

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Abstract
In sonicated human spermatozoa, phosphodiesterase hydrolyzed adenosine 3′:5′-monophosphate (cAMP) at 20.80 pL 3.23 nmoles/108sperm/20 min at 37°C (50 μM cAMP, initially). In human semen, about 60% of the phosphodiesterase activity was in the spermatozoa. Both polyacrylamide gel electrophoresis ind DEAE-cellulose column chromatography indicated that there are at least 5 isozymes of phosphodiesterase. Various steroids were tested at a concentration of 2 μg/ml for their effects on phosphodiesterase activity in semen. None was found to have any significant effect. In sonicated human spermatozoa, adenylate cyclase synthesized cAMP at 0.02-2.11 nmoles/108 sperm/20 min at 37°C (1 mM ATP, initially) depending on the availability of Mn2+ and caffeine in the assay mixture. Mn2+ was demonstrated to be a potent adenylate cyclase activator in human spermatozoa and its effect on human sperm adenylate cyclase was found to be dose-dependent. Cholera toxin, at a concentration of 20 μg/ml, had no effect on human sperm adenylate cyclase activity after it had been incubated with the intact spermatozoa for between 5 min and 5 h at 37°C before the sperm were homogenized and the rate of cAMP formation assayed. In addition, human sperm adenylate cyclase decayed rapidly at 37°C. Of various steroids tested at a concentration of 2 μg/ml for their effects on human sperm adenylate cyclase activity, only oestradiol-17β showed a significant effect, elevating the rate of cAMP formation by about 30%.