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LESTER PACKER 



an energy-linked form of the oxidation-reduction carriers arises, and that 

 this component is capable of giving rise to further intermediates which 

 interact with inorganic phosphate and adenosine diphosphate (ADP) 

 leading to adenosine triphosphate (ATP) synthesis. The reactants of the 

 system are clearly substrate, which may interact at different sites, and 

 oxygen for electron transport, and phosphate and ADP required for the 

 synthesis of ATP. It happens that these reactants are capable of inducing 

 characteristic changes in mitochondrial volume. The product of the 

 process, ATP, also can control mitochondrial volume but it appears to 

 have a rather special role. Very early in the study of the swelling-shrinking 

 phenomenon Raaflaub [3] and Brenner-Holzach and Raaflaub [4] reported 

 that swelling of rat liver mitochondria was retarded by ATP and also that 

 the state of swelling was correlated with the intramitochondrial content 

 of ATP. Dr. Lehninger and his associates [5, 6] have, of course, clearly 



Glutamate (5mM 



O, = 



7 9 



Time (mm) 



15 



Fig. 2. Effect of the reactants of respiratory chain phosphorylation in mito- 

 chondrial swelling and shrinking. 



shown that ATP acts as a potent agent to reverse swelling induced by 

 treating mitochondria with a wide variety of the reagents, but that reversal 

 of swelling appears to be most effective after some treatment of the mito- 

 chondria occurs which renders the membrane more permeable to this 

 substance. Thus reversal of swelling by ATP was found to be more effective 

 when mitochondria were suspended in potassium chloride rather than 

 sucrose solutions. Reversal of light-scattering changes in fragmented 

 mitochondrial membranes is also readily brought about by ATP [7]. The 

 fact that the reactants and product of this system under appropriate cir- 

 cumstances can interact with the swelling-shrinking phenomenon suggests 

 that the phenomenon is controlled by some common intermediate. An 

 example of rapid metabolically-driven volume changes in rabbit cardiac 

 muscle mitochondria is shown in Fig. 2. The apparatus employed was a 

 Brice-Phoenix light-scattering photometer adapted for recording with the 

 photomultiplier positioned at 90' to the incident beam at 546 m/.t. In some 



