D. W. VAN BEKKUM 

 IRRADIATION OF SPECIFIC ORGANS 



In this connection it is perhaps of interest to mention that we have not been 

 able to find any interference with the oxidative phosphorylation of mitochon- 

 dria isolated under similar conditions from the livers of irradiated rats. 

 Even a dose of 5,000 r administered to the liver region failed to produce an 

 effect as observed in the case of spleen and thymus mitochondria. Since 

 the liver is generally held to be a radio-resistant organ, these observations 

 suggest a relation between the disturbance of oxidative phosphorylation and 

 the radiosensitivity of the cells from which the mitochondria are derived. 



Because of the well known sensitivity of the spleen to various forms of 

 stress, it was considered essential to investigate the effect of radiation on the 



zn 



E 700 



Figure 5. Effect of intermittent hypoxia on oxidative phos- 

 phorylation of spleen mitochondria. Black bars : phosphate 

 uptake in [xmol/mgN ; white bars : oxygen uptake in 

 [I atoms/mg N ; C ; controls ; IH : intermittent hypoxia 



75 



SO 



25 



C IH 



I IH 



spleen only. To this end the spleen was exteriorized during irradiation 

 while the rest of the animal was being shielded. In this series the controls 

 were subjected to a sham-procedure. The depression of oxidative phos- 

 phorylation of the mitochondria isolated from the irradiated spleens was 

 found to be comparable to that observed after total body irradiation. The 

 interference with phosphorylating activity after total body exposure is 

 therefore at least for the greater part the result of the action of X-rays on 

 the spleen tissue itself. 



In vitro irradiation of isolated spleen mitochondria has been performed 

 both in the inactive state at 0° C and during incubation in the presence of 

 substrates and oxygen at 38° C. Following the irradiation the mitochondria 

 were kept at 0° C in the presence of versene for 4 hours and reincubated 



205 



