Effect of Insulin and Hexokinase on Glycolysis of Bovine Spermatozoa

Summary Insulin, yeast hexokinase, or a combination of both substances increased the rate of fructolysis of washed, phosphate buffer-suspended bovine spermatozoa. Seminal plasmas from the same ejaculates suppressed insulin-hexokinase effects. Glucose uptake was not affected by insulin, and hexokinase depressed it. Insulin and hexokinase together, however, increased glucolysis by sperm. When glucose and fructose were in the same media only the former was appreciably utilized and its uptake was increased by the insulin-hexokinase combination. The effect of hexokinase on fructolysis was not merely reversed by boiling the enzyme, but fructolysis was markedly depressed. In the presence of hexokinase, corticotropin, egg albumin, gonadotropin, or oxytocin did not increase the fructolytic rate, although oxytocin had a latent, depressant effect. Glucagon, like insulin, significantly stimulated fructolysis under similar conditions. The effects of insulin and hexokinase, observed in these experiments, cannot be explained in terms of our present knowledge.