8o 



ENZYMES AND DRUG ACTION 



that whilst dichlorophenol increases the rate of respiration 

 of Arhacia eggs, it decreases their rate of cleavage. In 

 such instances, when there are two or more cellular pro- 

 cesses which are interfered with in different ways by the 

 same drug, which is to be taken as the index of activity 

 on cellular enzymes ? There is no simple answer to this 

 question. Furthermore, if we endeavour to correlate the 



-2 



log [hCN] 



Fig. 15. The relationship between concentration of HCN and inhibition 



of various physiological processes, (a) Assimilation of CO2 by Chlorella; 



(b) oxygen comsumption of frog's ventricle; (c) mechanical response of 



frog's ventricle; (d) lethal action on Tribolium confusum 



amount of drug taken up with the change in a particular 

 activity, it is commonly found that there is no close 

 correlation. Fig. 14 shows, for example, that when phe- 

 nol is acting on yeast there may be a considerable uptake 

 of phenol before a significant change in physiological 

 activity is observed. The first moiety of the phenol taken 

 up appears to be inactive. 



It is thus clear that the action of drugs on intracellular 

 enzymes must be difficult to analyse. 



