RESPIRATION AND OXIDATIVE PHOSPHORYLATION 



115 



1956); it acts in low concentration, in some cases stoichiometrically 

 in relation to cytochrome b (Chance, 1952). In experiments on dog 

 and bull spermatozoa one finds a ratio of 2 to 3 antimycin molecules 

 per cytochrome b equivalent (6 X 10 5 antimycin molecules per cell). 

 This suggests that antimycin could be bound to components other 

 than electron carries as is the case in ascites cells (Chance and Hess, 

 1959). This hypothesis is supported by the fact that antimycin A 

 affects spermatozoan motility at concentrations lower than those re- 

 quired for inhibition of respiration. 



The addition of Amytal, in the presence of succinate, does not 

 lead to a significant change in the steady state of cytochrome re- 

 duction, and respiration is not inhibited (Fig. 8). Succinic acid 

 oxidation nevertheless utilizes the normal respiratory chain from 

 flavoproteins to cytochrome a 3 , as shown when azide is added to a suc- 



410| I | ' I l / ' |<50 mp 



Fig. 8. Difference spectra of bull spermatozoa at liquid nitrogen tem- 

 perature. Cells washed and suspended in RP, pH 7.2. Samples H4320 and 

 H512. (ix (solid line): (succinate 20 mM) — (endogenous substrates); both 

 aerobic. d 2 (dashed): (succinate, Triton 3 o/oo) — (endogenous substances); 

 both aerobic. b x (solid line): (succinate, Amytal 4 mM) — (Amytal 4 mM); 

 both aerobic. b 2 (dashed): (succinate, Amytal, azide 10 mM) — (succinate, 

 Amytal); both aerobic. Reduction by succinate in per cent: 3 (cyt a), 25 

 (c + c x ), 54 (b) in exp. a x . Apparent lower reduction of cyt c + c t in exp. 

 bi is due to Amytal effect on reference side. Reduction by azide in per 

 cent: 54 (cyt a), 57 (c), 32 (c x ), 64 (b). Percentages obtained by compari- 

 son with sample of same preparation where pigments were totally re- 

 duced by anaerobiosis or dithionite. 



