182 Discussion 



resistant to the drug even when repeatedly subcultured in its absence, 

 and without any genetic change having occurred. In other words, there 

 might be some normal metabolite which could maintain drug resistance 

 by some concentrating mechanism of the kind you described. 



Davis: Yes, I can imagine that a drug might induce an altered capacity 

 of the cell, or of a subcellular particle, to concentrate both the drug and 

 some substance in the environment other than the drug. Then on further 

 growth in the absence of the drug the other substance, which might be 

 a normal metabolite, could conceivably maintain the induced state. 



