128 The Biochemistry of Semen 



So far, however, the only instance other than semen, where hepta- 

 cosane has been shown to occur in the human body, is in the urine 

 of pregnant women. It is absent from the urine of men and of non- 

 pregnant women, and is devoid of oestrogenic activity. Nothing 

 is known about the origin or function of seminal heptacosane. 

 Should future investigations, however, show that heptacosane in 

 semen is involved in the metabolism of fatty acids or aldehydes, then 

 its fate would be analogous to that of plant hydrocarbons which 

 are well known to be associated with the metabolism of fatty acids, 

 aldehydes and alcohols in plants. 



Role of lipids in sperm jnetabolism 



The functional aspects of lipid metabolism in spermatozoa have 

 been the subject of investigations by Lardy and Phillips (1941«, b\ 

 1945). To begin with, these authors confirmed the observation 

 originally made by Redenz (1933) that, in contrast to whole semen 

 which can be stored successfully both anaerobically and aerobically 

 owing to the presence of glycolysable carbohydrate in the seminal 

 plasma, bull spermatozoa separated from the seminal plasma by 

 centrifugation and washing, can survive only in the presence of 

 oxygen. From this they inferred that when the spermatozoa are 

 deprived of sugar, they begin to oxidize aerobically some of their own 

 intracellular constituents as a source of energy for motility. To 

 detect the oxidizable substrate, sperm samples were analysed when 

 fresh and after periods of storage; it was then found that a period 

 of aerobic incubation of bull spermatozoa caused a significant de- 

 crease in the content of lipid phosphorus accompanied by an increase 

 in the acid-soluble phosphorus. But when glucose was added to the 

 washed sperm, the decrease in the phospholipid content of sperma- 

 tozoa was very slight, an indication perhaps, of a preference by 

 spermatozoa for the glycolytic mechanism as a source of energy 

 (Table 18). It was also found that certain phospholipids prepared 

 from egg-yolk, liver and soya bean, effectively maintained the 

 oxygen uptake and motility of washed sperm suspensions under 

 aerobic conditions; however, on the addition of sugar to the sperm 

 suspension, the phospholipids no longer produced an effect on 

 either respiration or glycolysis. 



In bull semen as ejaculated, with its large reserve of readily 



