150 LARS ERNSTER 



of dicoumarol on mitochondrial oxidative phosphorylation [29]. The 

 rational standpoint in view of the present conclusions would seem to be 

 that this effect is independent of the inhibitory effect of dicoumarol on DT 

 diaphorase. Alternatively, one could think that DT diaphorase, although 

 not taking part in the main pathway of terminal electron transport, might 



TABLE VII 

 Capacity of Various Quinones to Act as Terminal Electron Acceptors in 



SUBMITOCHONDRIAL DPNH OXIDASE, AND THE AmYTAL SENSITIVITY OF THESE 



Reactions 



(lirnster, Danielson and Conover, unpublished) 



The quinones were added in final concentrations of 0-04 mM. Oxygen uptake 

 in these systems was blocked with 03 mM cyanide. 



P . . "o inhibition 



Terminal electron acceptor by 2 mM 



activity , 



amytal 



play some accessory role, such as a regulation of the redox-state of the mito- 

 chondrial pyridine nucleotides, during coupling of respiration to phos- 

 phorylation. However, the fact that certain tissues, e.g. pigeon liver [21], 

 seem to contain very little or none of the dicoumarol-sensitive flavoenzyme, 

 and still exhibit a highly active phosphorylation, would seem to impose 

 serious obstacles to a consideration of this alternative. 



Activation of succinate oxidation and succinate-linked 

 reduction of DPN 



OBSERVATIONS WITH HIGH-ENERGY PHOSPHATE-DEPLETED MITOCHONDRIA 



I wish to begin the second section of my report by quoting a finding 

 that Dr. Low and I described in 1955 [33]. At that time we found (Fig. 7) 

 that rat liver mitochondria exposed to ageing in a phosphate-containing 

 medium lost some of their succinoxidase activity in the course of the ageing 

 process. The decrease was of a transitional character; upon prolonged 

 ageing, the mitochondria resumed their original succinoxidase activity. 

 We found, moreover, that the decreased succinoxidase activity could be 



