lOO F. A. HOLTON AND D. D. TYLER 



11. Holton, F. A., Biochetn.J. 6l, 46 (1955). 



12. Chance, B., and Baltscheffsky, M., Biochetn.J. 68, 283 (1958). 



13. Chance, B., and Packer, L., Biochem.J. 68, 295 (1958). 



Discussion 



Klingenberg : May I mention that the phenomenon of reversible swelling was 

 also reported some years ago by us for flight muscle mitochondria. These show, 

 with glycerolphosphate as substrate, a very pronounced reversible swelling which 

 can be related to respiratory control and to changes in the redox state of respiratory 

 components; in further unpublished studies we noted that with pyruvate plus 

 malate which are very effective respiratory substrates for mitochondria practically 

 no reversible swelling could be observed. Sometimes even contraction of the mito- 

 chrondria can be observed. Studies on the internal adenine nucleotide content 

 showed that the ATP to ADP ratio in mitochondria is the same whether one has 

 glycerolphosphate or pyruvate plus malate there. The difference in other nucleo- 

 tides can only be seen in the reduction of DPN or in the reduction of flavin nucleo- 

 tide, the glycerolphosphate reduces the DPN to a higher extent and the flavin also, 

 whereas pyruvate plus malate do not reduce the DPN or the flavin nucleotide to an 

 appreciable extent. 



Holton : Am I right in interpreting your feeling that the reactions important 

 in controlling structural state are at the flavin end and that they are not related 

 directly to the ATP-ADP equilibria inside the mitochondria. 



Klingenberg : Yes. 



Mitchell: You say. Dr. Holton, that this kind of swelling and shrinking, the 

 reversible kind, is quite diflFerent from the kind studied by Dr. Lehninger. Are you 

 in fact studying the same membrane ? There are two membranes here. Are you 

 quite sure that both these cases of swelling and shrinking are due to effects on the 

 same membrane ? 



Holton : I would say that the fact that the mitochondria that Dr. Lehninger 

 studies are a good deal further from the native state than ours is consistent with 

 your idea, since the reversible phenomena that both we and Dr. Packer study don't 

 last long. I suppose it might well be a more intact particle which shows the rever- 

 sible phenomena and one which has got holes in it which shows the other. 



Lehninger: I would just like to add that occurrence of two different morpho- 

 logical types of swelling could be a plausible resolution of the apparent differences 

 in the properties. It should be made clear that there is no disagreement as to the 

 observations. We have confirmed the effect of ADP on a tightly coupled system. 

 On the other hand Dr. Holton has confirmed our findings that ATP is specific for 

 shrinking drastically swollen mitochondria. As I pointed out in one of my slides 

 there are at least two diflferent ways in which mitochondria can swell and we have 

 suggested in fact that it may be the outer membrane which is the ATP-activated 

 structure. On the other hand damage to the membranes on drastic swelling could 

 produce a diflference in access of ATP and ADP, but it seems unlikely that a strict 

 ADP specificity will change to a strict ATP specificity on damaging a structure. 

 I would like to ask Dr. Holton a question which I think will contrast the different 



