Oxidative Phosphorylation in Irradiated Cells 87 



values obtained at 30 minutes and at 1 hour after irradiation 

 are pooled the differences between irradiated and control 

 preparations are found to be statistically significant both 

 in the case of phosphate and oxygen uptake. This demon- 

 strates an alteration of a mitochondrial function at a time 

 when nuclear degeneration is absent or limited to a few cells 

 only. Table III further shows that the cytochrome c effect 

 increases rapidly after the first hour, and that at 4 hours after 

 irradiation the very low phosphate uptake of the mito- 

 chondria is more markedly stimulated by added cytochrome c 

 than is the oxygen consumption. In this case cytochrome c 



Table III 



Influence of Total Body Irradiation (700 r) on the Cytochrome c 



Effect in Spleen Mitochondria* 



% stimulation by cytochrome cf 

 Hours after Phosphate uptake O^ uptake 



control irradiated control irradiated 



0-5 65(4) 77(4) 82(4) 95(4) 



1 63 (4) 86 (4) 66 (3) 91 (3) 



2 90 (4) 180 (3) 92 (4) 165 (4) 

 4 82 (2) 362 (2) 84 (2) 172 (2) 



* Mean values are presented, the number of experiments is given between brackets. 



t Stimulation is expressed in percentage of the values obtained in the absence of cytochrome 

 c. Substrate : succinate ; concentration of cytochrome c: 28 x 10 'M. The mitochondria were 

 washed twice with sucrose. 



nearly doubles the P/0 ratio. These results suggest that in 

 spleen mitochondria a relative cytochrome c deficiency 

 develops very shortly after irradiation. 



It was of course essential to know whether this reflects 

 an interference by radiation with some part of the cytochrome 

 system. It was not inconceivable that some radiation- 

 induced structural alteration of the mitochondria might cause 

 a leakage of cytochrome c during the isolation, in which case 

 washing of the mitochondria might be expected to increase 

 this leakage. In previous experiments with normal spleen 

 mitochondria it was found that repeated washing causes a 

 deficiency of DPN, which could be demonstrated in the 

 a-ketoglutarate system. 



To test the possibility of the occurrence of a similar leakage 



