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LESTER PACKER 



Therefore it may be anticipated that a small fluctuation in the concentration 

 of ADP would have a more extensive effect upon mitochondrial volume 

 than a similar change in phosphate. How about the extent of the reversible 

 volume changes ? When the metabolically induced changes are calibrated 

 by comparing them with an osmotically induced change in volume, then 

 the calculated magnitude of the metabolic changes is of the order of 20% 

 of their total volume [15]. It must, of course, be asked — can such changes 

 in mitochondrial volume be induced through fluctuations in the con- 

 centrations of the reactants of the respiratory chain in vivo ? If this is so, 

 what effect would this have upon metabolic reactions ? Perhaps in swollen 

 or shrunken states the ability of metabolites to cross the membranes is 



240 



120 5. 



6 

 60 











2 3 4 5 

 Time (min) 



Fig. 3. Respiration and light-scattering changes in Ehrlich ascites tumour 

 cells observed after mannose addition. The numbers above the upper trace refer 

 to the calculated rates of oxygen consumption in /xM/l./sec. 



changed. This would affect the competition which exists between cyto- 

 plasmic and mitochondrial compartments in the cell for the same meta- 

 bolite. Indeed, the membrane has been implicated as a possible site for 

 the regulation of certain effects in the intact cell such as the Pasteur and 

 Crabtree phenomena, which involve complex interactions between 

 different compartments in the cell. This subject was authoritatively dis- 

 cussed at the recent symposium on regulation of cell metabolism [18]. For 

 this reason it seemed promising to Dr. Colder and me [19] to attempt to 

 demonstrate light-scattering changes in ascites tumour cells following the 

 addition of certain carbohydrates. The rapid changes in metabolism which 

 characterize the early phases of the Crabtree effect have been probed in 

 detail by Chance and Hess [20]. Figure 3 demonstrates a simultaneous re- 

 cording of O2 consumption and light-scattering in a suspension of these 

 cells in Krebs-Ringer phosphate medium. Addition of mannose initiates an 

 acceleration of respiration lasting for several minutes, which is then 



