684 



6. aRsenicals 



Effects of Various Factors on Respiratory Inhibition 



Florijn and his collaborators (1950) at Groningen felt that the selective 

 inhibition of tumor cells by urethane and arsenite might be due to the higher 

 metabolic rates and energy requirements of tumor cells, and thus investi- 

 gated the effect of respiratory rate on the inhibitions. They varied the rate 

 by changing the oxygen tension and adding 2,4-dinitrophenol. Certain 

 aspects of these experiments have been previously discussed (page 1-861; 

 the results on kidney mince with 0.25 and 1.4 mM arsenite were shown 

 in Fig. 1-15-28). Huisman (1951) used lower arsenite concentrations and 



Fig. 6-5. Effects of arsenite at three different con- 

 centrations on the respiration of rat kidney mince 

 as influenced by the O2 tension. (Modified from 

 Huisman, 1951.) 



found stimulation of the respiration at low oxygen tensions (Fig. 6-5). 

 As was stated previously, the situation is perhaps too complex to allow 

 a simple interpretation, and these observations on respiratory stimulation 

 make the problem even more difficult. It is unlikely that the relationship 

 is simply one involving the respiratory rate, and it. seems more reasonable 

 to attribute the different degrees of inhibition to altered metabolic patterns, 

 the fraction of the respiration dependent on the keto acid oxidases and the 



