Stable Structural States of Rat Heart Mitochondria 



F. A. HoLTON* AND D. D. Tyler 



Medical Research Council, Experimental Radiopathology Research Unit, 

 Hammersmith Hospital, London, England 



Recent work of Packer [1,2] has shown that isolated mitochondria of 

 both hver and heart in dilute suspension may be induced to undergo 

 rapidly reversible changes in light-scattering properties and that the 

 direction of these changes is related to the relative concentrations of ADP 

 and ATP in the reaction medium. Changes in the light-scattering properties 

 of suspensions of mitochondria are commonly ascribed to alterations in the 

 structure of the individual particles. This hypothesis has been adopted by 

 Packer and is also assumed in what follows here. 



Rapidlv reversible changes in mitochondrial structure may also be 

 demonstrated in the absence of external adenine nucleotide [3], but lately 

 we have followed Packer in the use of externally added adenine nucleotide, 

 and in experiments with heart mitochondria we have confirmed many of 



TABLE I 



Ratios of Rates of Chax(;e of Extinction Observed in a Suspension of Heart 

 Mitochondria at 434 m/t and 477 • 5 mfj. in Response to Additions of Phosphate 



and Succinate 



Data calculated from Fig. i. The values given in the last column should be 

 compared with the theoretical ratio calculated from Rayleigh's law. The theoretical 

 ratio for measurements at 434 m^tt and 477 • 5 m/x where the changes of extinction 

 are due solely to changes in the light-scattering properties of the material is i -47. 



* Present address: Royal J^tterinarv College, Royal College Street, London, 



X.IV.T. 



