METABOLIC CONTROL OF STRUCTURAL STATES OF MITOCHOXDRLA 93 



swelling occurs apparently the ATP has the ability to bind on the membrane or 

 penetrate whereas before it was ineffective. I think that ATP and ADP act through 

 some common mechanism by influencing energy-linked intermediates. With regard 

 to the KCl comment Jackson and Pace have shown that the half time for penetra- 

 tion of KCl is seconds whereas for sucrose it is hours. 



Lehninger : If this is the case then ATP leaks very readily. 



Packer: Yes. However, this may not be so in vivo. 



Lehninger: In view of what you say I am therefore a little puzzled over those 

 explanations of the Pasteur reaction which are based on " compartmentation " 

 of ATP. 



P.\CKER : Well the reconstruction experiments indicate that the leakage of ATP 

 through the membrane is rate-limiting. If we assume that in the course of isolation 

 of mitochondria from the tissue some swelling has taken place it is reasonable that 

 this property of the escape of .ATP is now retained to a lesser extent, but still 

 sufficiently to detect it. 



Hess: If one isolates the mitochondria from glucose ascites cells then it is 

 apparent that they take in quite a lot of ATP in comparison with mitochondria 

 isolated from ascites tumour cells which do not contain glucose. Now the shrinkage 

 of mitochondria seems to be associated with the retention of .ATP as far as the 

 experimental data are concerned. It is worthwhile to point out that cytologists have 

 evidence about mechano-proteins in living cells and have found in a number of 

 cells contractile proteins in the cytoplasm which can be readily activated by the 

 addition of ATP. My question is: there is a certain discrepancy in the interpreta- 

 tion in the Crabtree effect ; what is the rate-limiting material which controls rate 

 of respiration whether phosphate or .ADP ? .As far as I see from your data if you 

 have low inorganic phosphate concentration, mitochondria are swollen and if you 

 have a low ADP concentration then the mitochondria are shrunk. Xow could you 

 draw any conclusions from your experiments on this point ? 



Packer : We have been interested in trying to examine the effect of phosphate 

 on the ascites cell with respect to the scattering problem. In this connection we 

 have tried to prepare phosphate-free ascites cells, but apparently we have not yet 

 been able to remove sufficient phosphate to lower the endogenous respiration, so 

 I don't feel that we have been able to put the effect of phosphate on the shrinkage 

 phenomenon to the test. 



Siekevitz: 1 wish to recall the experiments Dr. Potter and I did in relation to 

 the amount of ATP available in mitochondria under conditions of oxidative 

 phosphorylation. When we added hexokinase we obtained the phosphate of the 

 ATP as glucose 6-phosphate in the medium. Under these conditions, we found 

 that the hexokinase does not attack the ATP inside the mitochondria but the ATP 

 coming out. So under these conditions of active phosphorylation, I do not know 

 whether the mitochondria are shrunken or swollen, but the .ATP can come out 

 very fast indeed. 



Ch.'\nce: Just a very short comment on the ability of .ATP rapidly to enter the 

 mitochondria. With tightly coupled mitochondria ATP can enter rapidly and at 

 the same time cause them to swell (unpublished observations). 



EsTABROOK : On the point of the comparison of rates of ATP getting out of the 

 mitochondria and ADP going back in, one can show using the coupled hexokinase 



