The role of oxidative phosphorylation in the generation of ATP in human spermatozoa

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Abstract
Washed human spermatozoa had an endogenous O2 uptake of 2.14 .+-. 0.17 nmol O2/108 spermatozoa per min (mean .+-. s.e.m. [standard error of the mean]; 35) which was stimulated by succinate (Vmax = 9.64 .+-. 0.44 nmol O2/108 spermatozoa per min) but not by other substrates. The ATP concentration in freshly washed spermatozoa was 12.18 .+-. 0.54 (s.e.m.) nmol/108 spermatozoa (26) and was maintained for 2 h in the presence of 2 mM D-glucose but fell to 9.56 .+-. 0.73 (s.e.m.) nmol/108 spermatozoa (13) in its absence. The presence of 2 .mu.M antimycin A, 2 .mu.M rotenone, 0.4 .mu.M carbonyl cyanide m-chlorophenyl hydrazone or 8 .mu.M oligomycin caused the ATP concentration to fall to < 2 nmol/108 spermatozoa but their effect was partly alleviated by 2 mM-glucose. Sodium malonate (5 mM) prevented the stimulation of respiration by succinate but had no effect on the APT concentration of the spermatozoa or their ability to produce 14CO2 from [uniformly labeled-14C]glucose. The least active of the tricarboxylic acid cycle enzymes was 2-oxoglutarate dehydrogenase (EC 1.2.4.2) (3.1 .+-. 0.6 (s.e.m.) nmol substrate transformed/108 spermatozoa per h (4). Cytochrome c oxidase (EC 1.9.3.1) was much less active than in rat spermatozoa (22.3 .+-. 6.0 (s.e.m., (4) and 615 .+-. 87 (4) nmol transformed/108 spermatozoa per min). Human spermatozoa apparently can obtain ATP by the respiration of endogenous substrate but the substrates and metabolic pathways involved remain obscure.