170 F. Dickens, G. E. Clock and P. McLean 



activity. The proportion of G6P metabolized by the glycolytic 

 route is not greatly affected, although there is a significant 

 increase in the small proportion oxidized by the pentose P 

 pathway. These findings emphasize the magnitude of G6Pase 

 activity in liver and its importance in controlling pathways of 

 glucose metabolism. The effect of various hormonal treat- 

 ments and of tumour formation on the activity of the pentose 

 P pathway has been assessed both by determination of 

 individual enzyme activities and also by the use of labelled 

 glucose. Although C-l/C-6 quotients are of doubtful quanti- 

 tative significance, alterations in this quotient in any one 

 tissue from animals under different physiological conditions 

 gives some qualitative indication of the relative activities of 

 the glycolytic and pentose P pathways. Unfortunately, 

 results obtained with the isotope method do not always 

 corroborate findings on enzyme activities, thus emphasiz- 

 ing the necessity for determining the overall activities of 

 metabolic pathways in addition to the activities of single 

 enzymes. Results obtained for liver from normal, diabetic 

 and hyperthyroid rats and for precancerous liver tissue, 

 DAB -induced hepatomata and embryonic liver are given in 

 Fig. 6 and Table III. 



Table III 

 Yields of ^^COg from [1-i*C]glucose and [6-i*C]glucose 



BY LIVER AND LIVER TUMOUR SLICES FROM RATS 



Percentage conversion to ^^CO^ 



Data from Agranoff, Brady and Colodzin (1954); Glock, McLean and 

 Whitehead (1956). 



