CHAPTER 



EVALUATION OF METABOLIC 

 PATHWAYS 



Our attention shifts in this chapter to a subject arising 

 out of the previous discussion, namely, an answer to the 

 question how to tell how much each given avenue of 

 metabolism is employed in the normal cell. In other words, 

 have traffic counting techniques been established, are they 

 reliable, and what do the counts show? The answers to 

 these questions are varied and almost too numerous; this 

 tends to reflect incomplete satisfaction with many of the 

 methods so far developed. 



Metabolic inhibitors, or "traffic blocks," have been used 

 from time to time to study metabolic pathways. They can- 

 not be used satisfactorily to study the pentose cycle because 

 suitable specific inhibitors of this cycle have not been de- 

 veloped. Beyond this, it is questionable whether their use 

 would be warranted even if appropriate inhibitors were 

 developed, since it cannot be readily determined whether 

 the unphysiological conditions that would result from the 

 accumulation of metabolites might introduce spurious 

 readings of the "traffic count." 



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