Effect of Addition of Fructose and of Glucose on the Fructolysis and Motility of Human Semen

The influence of substrate concentration on the fructolysis of human semen was determined directly by the addition of fructose and of glucose to incubated semen specimens. The addition of fructose resulted in a marked increase in fructose utilization and lactate production with two moles of lactate recovered for each mole of fructose utilized. Added fructose depressed motility in the presence of disodium phosphate buffer but not in the presence of Ringer's solution or of a complex phosphate buffer. The addition of glucose resulted in a marked decrease in fructose utilization with no effect on motility. Simultaneous measurement of fructose and of glucose utilizations revealed that the glucose utilized was approximately equal to the decrease in fructose utilization and that the increase in glycolysis, expressed as total sugar utilization, was the same when an equal amount of either fructose or glucose was added. These data indicate that the glycolysis of human semen is substrate-limited and that glucose is a competitor of fructose and displaces it mole for mole in this system. Submitted on May 9, 1958