ASPECTS OF METABOLISM OF SPERMATOZOA 135 



The relative importance of different substrates as energy sources 

 is a subject with some interesting ramifications. Vantienhoven et al. 

 (1952) reported that glucose was used in preference to fructose by 

 bull spermatozoa, and we have confirmed this finding with C 14 - 

 labeled glucose and fructose. Our studies with octanoate-1-C 14 , how- 

 ever, provide a different picture of substrate relationships (Flipse, 

 1960b). As shown in Table II, spermatozoa incubated with a con- 

 stant amount of octanoate- 1-C 14 but an increased concentration of 

 carrier octanoate produced C 14 2 of reduced specific activity — the 

 well-known isotope dilution effect. When unlabeled glucose re- 

 placed the unlabeled octanoate, a much smaller reduction in specific 

 activity of C0 2 occurred, indicating that octanoate utilization is rel- 

 atively independent of the presence of glucose. Perhaps more sur- 

 prising was the observation that substitution of unlabeled acetate 

 for unlabeled octanoate caused only a moderate reduction in specific 

 activity of C0 2 . 



We have been reminded in this symposium of species-related dif- 

 ferences in morphology of spermatozoa, and certain species-related 

 differences in metabolism have been presented as well. It is impor- 

 tant, of course, that we specify the species when discussing the im- 

 portance of a particular metabolic reaction. It is also important to 

 note the condition of the preparation being used; Dr. Salisbury has 

 presented data clearly illustrating this point. I am often reminded 

 of an experience in our laboratory a few years ago when we were 

 studying spermatozoan metabolism of glucose-C 14 . We were using 

 washed sperm in these studies, and it so happened that on one oc- 



Table II. Production of C 14 2 from octanoate- 1-C 14 by washed bovine 

 spermatozoa during 1 hour of incubation at 37°C in modified Ringer's so- 

 lution pH 7.2 a 



Concen- "" Unlabeled Substrate 



tration (counts per minute per micromole of C 14 2 ) 



Octanoate Glucose Acetate 





 1 

 5 



Data from Flipse (1960b). 



