EFFECTS OF RESPIRED 

 OXYGEN— RADIO-PROTECTIVE ACTION OF 

 CERTAIN AMINES— (/») RAT LYMPHOCYTES 



(in vivo) 



Ruth Moore and H. A. S. van den Brenk 



Radiobiological Research Unit, Cancer Institute Board, 



Alelbourne 



Rat lymphocytes, in vivo and in vitro, have been used as a radiobiological 

 indicator for the study of cjuantitative effects in non-dividing but radio- 

 sensitive cells^' -' ^•'*. The ratio of degenerating to normal cells at a pre- 

 determined time after irradiation can be used as a measure of radiation 

 damage. Clearly obsei'vable pyknotic changes are visible within a few hours 

 of irradiation, the time of onset of pyknosis varying from cell to cell. 



Using explanted rat lymph nodes, TrowelP demonstrated that an increase 

 in oxygen in the irradiated medium caused an increase in radio-sensitivity, 

 which, at 100 per cent oxygen tension, was twelve times that for the anoxic 

 state. Patt et al.^ showed that cysteine had a protective action on irradiated 

 rabbit thymocytes in vitro in the presence of oxygen. 



The experiments described below were designed to determine the influence 

 in vivo on the irradiation of rat lymphocytes of: 



(/) two radio-protective agents, cystamine and 5-hydroxytryptamine 



(5-OHT) 

 {2) changes in respired oxygen pressure 

 [3] the effect of I'espired oxygen tensions on the chemical protection. 



MATERIALS AND METHODS 



The rats used were from a Canberra black stock, weighing between 60 and 

 70 g. _ 



Cystamine and 5-hydroxytryptamine in aqueous solution were injected 

 intraperitoneally 7 minutes before irradiation. The rats were irradiated 

 with 400 r X-rays, whole-body dose, in a specially-designed pressure tank, 

 described in the previous paper. 



At a fixed time after irradiation, the rats were killed by cervical fracture, 

 and two lumbar and one sacral lymph nodes were dissected out. Each node 

 was used to prepare a film using the technique of Trowell". The time between 

 killing the rats and fixing the films was from 7 to 10 minutes. 



Each slide was coded to eliminate subjective error, and 500 small lympho- 

 cytes were counted and scored for each film. Previous experiments carried 

 out had shown that when nodes were fixed 5 hours after treatment, pyknotic 

 cells present were mainly in the later stages of degeneration, and the presence 

 of a considerable number of chromatin fragments made accurate counts 



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