126 PIERRE H. GONSE 



the molecular ratio between antimycin and cytochrome b, at 85% 

 inhibition of respiration, is 2:1 in dog sperm, and therefore one 

 could assume that the extra molecule of antimycin is first bound to 

 a site which is more closely related to energy conservation, e.g., a 

 transphosphorylating reaction, than to electron transfer. The addi- 

 tion of glucose, as in the case of Amytal, entirely reverses the inhibi- 

 tion of motility. No titration curves are available on Spisula sperma- 

 tozoa. However, ethanol, which is currently used as a solvent for 

 antimycin A, activates respiration of these spermatozoa when the 

 concentration of alcohol exceeds 1%, a phenomenon not observed in 

 dog sperm. Furthermore, in Spisula sperm, 2.5% ethanol produces 

 a complete inhibition of motility. However, with 1.85 X 10~ 6 M anti- 

 mycin A (final ethanol concentration 0.75%) an inhibition of 50% 

 of respiration is observed. This indicates an antimycin sensitivity of 

 respiration in agreement with data of Bonner (1961) who found that 

 the (b) cytochromes of scallops and Spisula muscles are both reduced 

 by antimycin A. 



From experiments with DNP, differences between spermatozoa 

 from invertebrates and mammals are most clearly revealed. Sensi- 

 tivity to the uncoupler varies widely (Fig. 18). In washed bull sper- 

 matozoa the average maximum activation of respiration by DNP is 2 

 times, with the optimum concentration of DNP 0.1 to 0.2 mM, when 

 lactate has been added as substrate. With lightly washed dog sperm, 

 the maximum activation was only 1.3 times normal respiration, 

 which, however, is probably more significant than the higher effect 

 found in bull. In Spisula spermatozoa the average of six experiments 

 shows an activation of 6.8 times (up to 8.5 times in two samples). An 

 experiment carried out on sperm of a different species of clam, Venus, 

 yielded analogous results (Fig. 18). The optimum concentration of 

 DNP for activation of respiration is 0.05 mM, lower than in either 

 dog or bull sperm. 



Motility in the spermatozoa studied is progressively inhibited at 

 DNP concentrations which activate respiration, 0.02 to 0.12 mM in 

 Spisula and 0.05 to 0.5 mM in dog sperm. Sensitivity varies widely, 

 however; in Spisula sperm, motility can be completely arrested while 

 in dog sperm a fair motility persists even in 1 mM DNP, so long as 

 oxygen is present. Glucose completely reverses the partial inhibi- 



