DISCUSSION 



has been observed. The effect has also been found after irradiation of the 

 exteriorized spleen only, but could not be produced by in vitro irradiation 

 of mitochondria. 



The decrease of phosphorylation is not secondary to the increased ATP-ase 

 activity and develops prior to the depression of anaerobic glycolysis, which 

 are observed in spleen homogenates after total body irradiation. 



The sensitivity of oxidative phosphorylation as well as its relatively rapid 

 impairment after irradiation suggest that this cytoplasmic lesion may be 

 intimately connected with the primary radiation injury. 



REFERENCES 



1 Trowell, O. a. J. Path. Bad. 1952, 64 687. 



2 Mole, R. H. Brit. J. Radiol. 1953, 26 234. 



3 Potter, R. L. and Bethel, F. H. Federation Proc. 1952, 11 270. 



* VAN Bekkum, D. W., Jongepier, H. J., Nieuwerkerk, H. T. M. and Cohen, J. A. 



Trans. Faraday Soc. 1953, 49 329. 

 '" Maxwell, E. and Ashwell, G. Arch. Biochem. Biophys. 1953, 43 389. 

 " VAN Bekkum, D. W., Jongepier, H. J., Nieuwerkerk, H. T. M. and Cohen, J. A. 



Brit. J. Radiol. 1954,27 127. 

 ^ Ashwell, G. and Hickman, J. Proc. Soc. exp. Biol. Med. 1952, 80 407. 



8 Ashwell, G. and Hickman, J. J. Biol. Chem. 1953, 201 651. 



9 Dubois, K. P. and Petersen, D. F. Amer. J. Physiol. 1954, 176 282. 

 10 Hickman, J. and Ashwell, G. J. Biol. Chem. 1953, 205 65 1 . 



DISCUSSION 



R. H. Mole : I am sure van Bekkum is right in deciding to look for biochemical 

 changes in the first few hours after irradiation. As he points out, at a time when 

 there is visible cell death in the tissue examined, biochemical changes must be occur- 

 ring from the fact of cell death alone. But in the light of this I wonder why he chose 

 as long an interval as 4 hours since by that time cell death in the spleen is quite 

 evident. 



I would also like to suggest that changes in oxidative phosphorylation by mito- 

 chondria may be analogous to the morphological changes in cell nuclei which follow 

 irradiation, and may be a consequence of lethal damage to the cell rather than the 

 cause of it. Just as nuclear pycnosis occurs in radio-sensitive organs and not radio- 

 resistant organs like muscle, so oxidative phosphorylation is altered in the spleen, 

 but not in the muscle (as Laser mentioned). If there is one thing clear about the 

 effects of whole body irradiation it is that some organs are radiosensitive and some 

 are resistant. If there is a biochemical lesson due to irradiation — and a biochemical 

 lesson there surely must be — then it seems to me it must be sought in the specific 

 biochemical activities which distinguish radio-sensitive from radio-resistant tissues, 

 not in the general metabolic properties which are common to all cells. 



209 



