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Discussion 



Chance : I should be glad to clarify an ambiguity which Prof. Slater pointed to ; 

 in the experiments published in the work with Hollunger, we had pretreated the 

 guinea-pig kidney mitochondria with glutamate. Therefore some ATP was pro- 

 duced by the a-ketoglutarate step. The addition of succinate therefore produced a 

 rapid and complete reduction of DPN. For the last 8 to 10 months we have been 

 working with pigeon-heart preparations which, when freshly prepared or after a 

 day's ageing, do have a ATP requirement for DPN reduction in the presence of 

 succinate. They will respire slowly but the DPN will not be reduced unless you 

 add ATP. If they are suspended in a medium containing phosphate, the respir- 

 ation will increase and the DPN will slowly be reduced in several minutes. Thus 

 this preparation is admirably suited to separate the substrate and energy require- 

 ments for the DPN reduction. 



Slater : I think there must still be some difference between our rabbit-heart 

 sarcosome preparation and your pigeon-heart preparation because 90 sec. at o' is 

 probably a short time. 



Chance: Yes; I think it is a question of endogenous substrate concentration. 



VOL. II. — Q 



