52 The Biochemistry of Semen 



Aerobically, in the presence of both fluoride (0 02m) and pyruvate 

 (001m), bull spermatozoa consume less oxygen than without 

 fluoride; this low rate of oxygen uptake can be enhanced by the 

 addition of 2 : 4-dinitrophenol (10~*m), which brings about a more 

 complete oxidation of that fraction of pyruvate which is not reduced 

 to lactic acid. Melrose and Terner (1952, 1953) claim that bull 

 semen can be graded according to the respiratory response of washed 

 spermatozoa to a system made up of fluoride, pyruvate and dini- 

 trophenol, and that in highly fertile samples the oxygen consumption 

 is low in the presence of pyruvate and fluoride, but is increased two- 

 fold or more, by the addition of dinitrophenol. 



Among substances which can provide exogenous material for 

 sperm respiration are glycolysable sugars and lower fatty acids such 

 as lactic, pyruvic and acetic acid (Fig. 10) but the species differences 

 in this respect are very marked. Thus, while in mammalian sperma- 

 tozoa for example, it is possible to prolong the respiratory activity 

 for a considerable length of time with glucose, fructose, mannose, 

 L(+)-lactate, pyruvate, propionate, butyrate, and oxaloacetate 

 (Lardy and Phillips, 1944, 1945; Mann and Lutwak-Mann, 1948; 

 Humphrey and Mann, 1949; Tosic and Walton, 1950; Melrose and 

 Terner, 1953), the respiration of oyster spermatozoa is increased by 

 a-oxoglutarate and oxaloacetate, decreased by acetate, propionate 

 and butyrate, and remains unaffected by lactate, glucose, fructose 

 and mannose (Humphrey, 1950). It appears also that the mode of 

 action of several organic acids on the respiration of mammalian 

 spermatozoa differs fundamentally from the influence exerted by the 

 same substances on the sperm of lower animals. This is illustrated 

 best by the example of the peculiar response of sea-urchin sperm 

 to malonate (003m), which was reported by Barron and Goldinger 

 (1941/)) to increase both the O2 uptake and the aerobic CO2 output 

 of sperm by as much as 200%. Succinic acid is another example of a 

 substance which was found to be highly effective in the respiration 

 of sea-urchin sperm (Barron and Goldinger, \94\a; Goldinger and 

 Barron, 1946) but has little effect on the oxygen uptake of intact 

 mammalian spermatozoa. Another characteristic difference in be- 

 haviour between sea-urchin and mammalian sperm concerns the 

 effect of the fatty acids on the initial rate of sperm respiration. In 

 the case of sea-urchin spermatozoa, the addition of a fatty acid salt 



