Under the aerobic conditions of these experiments, dilution of bovine semen with phosphate ion depressed oxygen consumption and motility of sperm cells. However, fructose utilization and lactic acid accumulation were increased in the presence of phosphate ion. When semen was diluted with isotonic sodium chloride oxygen uptake was greater, motility was maintained better and fructose utilization and lactic acid accumulation were lower than in the phosphate-diluted semen.
Twice-washed cells in a diluent containing seminal plasma utilized more fructose and accumulated more lactic acid than those in plasma-free diluent. The depressive effect of phosphate on respiration was not due to H2O2 formation nor to changes of osmotic pressure.
The season of the year in which semen was collected influenced its metabolic response in each of the diluents studied. The presence of glucose-6-phosphate dehydrogenase activity was not conclusively demonstrated in cell-free extracts of bovine spermatozoa prepared by sonic oscillation.