Oxidation of exogenous substrates by isolated human spermatozoa

¹ Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts

In view of the uncertainty whether human spermatozoa display a true oxidative activity, this question was reinvestigated with the aid of C¹⁴-labeled substrates. The spermatozoa were isolated from the seminal plasma by centrifugation and resuspended in calcium-free phosphate saline. The radioactive CO₂, produced during aerobic incubation of the sperm suspension with C¹⁴-labeled glucose, pyruvate or acetate, was collected and from its amount and radioactivity the rates of oxidation to CO₂ and H₂O of the various substrates were calculated. The results show that of the three substrates tested glucose and pyruvate were oxidized more readily than acetate. The addition of 10^–4 m 2:4-dinitrophenol resulted in the acceleration of the rates of oxidation of glucose and of pyruvate, but had no inhibitory effect on the oxidation of acetate. These observations are evidence of the existence of an actively functioning oxidative enzyme system in human spermatozoa.