IONIC AND OSMOTIC CONDITIONS 65 



schild and Barnes, 1954b). These data, coupled with metabolic data 

 shown in Table I and Fig. 1 and other data to be presented, are in- 

 terpreted as indicating either that sodium ion has a marked stimula- 

 tory effect or that potassium has a marked inhibitory effect on me- 

 tabolism of mammalian spermatozoa. The latter view seems to fit 

 more satisfactorily the observations (Cragle and Salisbury, 1959). In 

 view of these striking facts we elected, first of all, to study the in- 

 fluence of these bulk cations and some of the anions found in the 

 reproductive tracts as possible mechanisms of natural control of 

 spermatozoan motility and metabolism. 



EXPERIMENTAL MODIFICATION OF AEROBIC METABOLISM 



Osmotic Pressure 



Relatively few experiments uncomplicated by the nature of the 

 ions and other particles exerting the pressure have been conducted 

 to measure the effect of osmotic balance of the suspension medium 

 on the aerobic and anaerobic metabolism of spermatozoa. Several 

 studies (Foote, 1950; Rothschild and Barnes, 1954a, b; Pursley and 

 Herman, 1950; Salisbury et al., 1948) have shown that most of the 

 media first widely used for artificial insemination were hypertonic 

 as compared to bovine seminal plasma. The fact of fertility from 

 their use suggests that the item is not critical. In fact, the studies of 

 Pursley and Herman (1950) indicate that for optimum livability of 

 sperm stored at temperatures above freezing, the freezing point de- 

 pression of the suspension media may vary from — 0.44 to — 0.66°C 

 (equivalent to about 235 to 360 milliosmoles). 



However, the aerobic metabolism of bull spermatozoa responds 

 differently to variations in osmotic pressure depending on the ions 

 exerting that pressure. The milliosmole concentration of the solu- 

 tions used in the following experiments has been controlled not only 

 by calculations of the solutes involved but also by measurement of 

 that concentration with a Fiske osmometer. In the first experiment 

 reported here (Cragle and Salisbury, 1959) the solutes were a com- 

 bination of fructose as substrate, and sodium and potassium citrates 

 and bicarbonates, with the milliosmole concentration varying from 

 150 to 392 for suspension of washed cells at a final concentration of 

 about 2.0 X 10 8 cells/ml. The results in Fig. 2 for a 2-hour period 



