The metabolism of pyruvate in bull spermatozoa

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Abstract
The endogenous respiration of washed spermatozoa of good motility from different bulls varied from -ZO2 6-28. F (0.02[image]) and 10-4 [image] 2,4-dinitrophenol (DNP) inhibited the endogenous respiration, especially when this was high. Classified as good were samples which gave little increase in O2 consumption with pyruvate and large increase with 2,4_dinitrophenol (DNP); as intermediate, where pyruvate increased respiration about half the rate for pyruvate plus DNP; and poor, where DNP caused no further increase in respiration, irrespective of whether pyruvate alone increased respiration. In samples with low endogenous respiration DNP in the presence of pyruvate increased the O2 consumption despite some inhibition of pyruvate utilization. In samples with high endogenous respiration, DNP did not stimulate the respiration in the presence of pyruvate. It strongly inhibited the oxidative removal of pyruvate. F inhibited the endogenous respiration and the oxidative removal of pyruvate to approx. the same extent as DNP. The effects of the 2 inhibitors were not additive. In the presence of F and pyruvate DNP stimulated the respiration of certain samples in which, without F, it was inhibitory. Chemical analysis showed that these samples oxidized pyruvate with low O2/net pyruvate ratios ( < 1) (net pyruvate - pyruvate utilized - lactate formed) and that DNP increased these ratios to 2.0-2.5. Other samples metabolized pyruvate with higher 02/net pyruvate ratios, which in some cases approached 2.5, and DNP caused a smaller or no further increase of respiration. 60 sperm samples of good motility from 16 bulls, tested in the presence of F, could be grouped according to the type of their respiratory response to pyruvate and pyruvate + DNP. A correlation appeared to exist between the metabolic behavior of sperm samples under the exptl. conditions described and the fertility of their donors as computed from their breeding record in artificial insemination.