Studies on the metabolism of semen. 4. Aerobic and anaerobic utilization of fructose by spermatozoa and seminal vesicles.

Previous studies on the metabolism of semen have furnished evidence that the reducing carbohydrate in seminal plasma is fructose, which is readily converted by the spermatozoa to lactic acid, thus providing an important source of energy for the sperm cells (Mann, 1946a, b, c). The rate of fructolysis represents an accurate and at the same time simple means of evaluation of semen; the fructolysis index (mg. fructose utilized by 109 spermatozoa in 1 hr. at 370) in normal bull and ram semen is 14-2-0, while semen with poor sperm motility gives much lower index values; azoospermic and necrospermic semen was shown to be altogethet unable to metabolize fructose (Mann, 1948a, b). Fructose originates in the accessory glands of reproduction, mainly the seminal vesicles, but in some species it is found also in the ampullae and in certain parts of the prostate organ (Mann, 1946c; Davies & Mann, 1947). The process of fructose formation is initiated and controlled by the testicular hormone; a hormonal deficiency due, for example, to castration, causes invariably a decrease or disappearance of seminal fructose, but treatment with testosterone promptly restores the ability of the accessory glands to produce fructose (Mann & Parsons, 1947). In this paper it will be demonstrated that fructolysis is a characteristic feature of both the aerobic and anaerobic metabolism ofsemen. Unlike spermatozoa, the seminal vesicles will be shown to lack the ability to utilize fructose anaerobically. Finally, the position will be discussed of fructolysis in relation to glucolysis and respiration, in both semen and seminal vesicles.