Factors Affecting the Metabolism of Acetate and Glucose by Ram and Bull Spermatozoa

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Abstract
The K and Mg concentrations of the suspending medium influenced the relative ease with which ram spermatozoa oxidized acetate and glucose. In the absence of K or Mg from the diluent acetate was usually oxidized at a lower rate than glucose and the oxygen uptake was correspondingly lower. The presence of 5-15 m[image] KC1 stimulated the oxidation of acetate to a greater extent than that of glucose and in a medium containing K the rate of acetate oxidation usually approximated or exceeded that of glucose. Potassium also stimulated anaerobic glycolysis and must affect the Embden-Meyerhof pathway as well as the Krebs-cycle reactions in ram spermatozoa. While Mg by itself did not influence the rate of oxidation of either acetate or glucose it suppressed the stimulatory effect of K on glucose metabolism. The use of a high phosphate (80 mM) diluent makes any differential effect of K on the oxidation of acetate and glucose difficult to observe since it depressed the oxidation of both substrates, presumably due to an effect on the tricarboxylic acid cycle. Natural variability in the relative case of oxidation of acetate and glucose may depend on the K and Mg levels in ram spermatozoa which are likely to vary from one ejaculate to another, with the extent of washing and the concentration of the cations in the suspending medium. Bull spermatozoa always oxidized glucose more readily than acetate, irrespective of whether K and Mg were added to the diluent. Bull spermatozoa would also seem to differ from ram spermatozoa in the fact that K stimulated glucose and acetate oxidation to approximately the same absolute amount. Furthermore, Mg did not inhibit the stimulating effect K had on glucose oxidation.