PHOSPHORYLATING ACTIVITY OF MITOCHONDRIA AFTER TOTAL BODY IRRADIATION 



{2) The ATP-ase activity of isolated spleen mitochondria after total body 

 irradiation has been found to be normal even at 24 hours after irradiation, 

 in the presence of a severely impaired phosphorylating capacity which was 

 observed in samples of the same preparation {Figure 8). 



We have also investigated if the decrease of anaerobic glycolysis which 

 has been described in mouse spleen homogenates at one day and longer 



^ I/O 

 o 



E 



20 

 W 



$ 



J 



C ^'K 



C 2'/\ 



Figure 8. Phosphate uptake and ATP-ase activity of 

 mouse spleen mitochondria at various periods after total 

 body irradiation with a dose of I,100r. Black bars: 

 phosphate uptake in pimol/mgN; hatched bars : ATP- 

 ase activity in (jimoI/mgN of phosphate formed 



after irradiation (Hickman and Ashwell^*'), has any relation to the disturb- 

 ance of oxidative phosphorylation. The fact that a normal rate of glycolysis 

 was observed in the presence of a decreased oxidative phosphorylation 

 {Figure 9) indicates that different mechanisms are probably involved in the 

 development of these two types of radiation damage. 



In conclusion there is as yet no evidence of the depression of oxidative 

 phosphorylation being secondary to some other known radiation-induced 



Figure 9. Oxidative phosphorylation of 

 spleen mitochondria and anaerobic gly- 

 colysis of spleen homogenates after total 

 body irradiation with a dose of 700 r. 

 Black bars : phosphate uptake in [jimol/ 

 mgN [left ordinate) ; white bars : oxygen 

 uptake in [j,atoms/mgN {left ordinate) ; 

 hatched bars : lactate formation in [jimol/ 

 ingN [right ordinate) 



> 60 



3-50 

 o 



E 



30 



20 



10 



L 



CD 



r2i 



o 



W E 

 8 ^ 

 6 

 if 

 - 2 



C 



2K 



U\ 



biochemical alteration. Therefore the effect must be ascribed to some block 

 in the oxidation-coupled phosphorylating reactions, the exact nature of 

 which is at present little understood. 



SUMMARY 



The depression of oxidative phosphorylation of mitochondria isolated from 

 spleen or thymus has been found to occur after doses as low as 50 r. This 

 biochemical change develops within a few hours after irradiation and a 

 close parallelism with the appearance of morphological changes in the nuclei 



208 



