EFFECTS ON RESPIRATION AND GLYCOLYSIS 



303 



that as respiration is depressed, lactate formation is accelerated. This 

 cannot be attributed to an action on the EM pathway, since anaerobic 

 glycolysis is depressed, or in the brain slices is unaffected. The most ob- 

 vious explanation is a primary inhibition of oxidative processes by mal- 

 eate and, since pyruvate and a-ketoglutarate oxidations have been shown 



20 



MALEATE + PYRUVATE 



MALEATE 

 MALEATE + 6LUTAMATE 



+ PYRUVATE 



MALEATE + GLUTAMATE 

 CONTROL 



Fig. 2-2. Effects of maleate on the respiration and aerobic gly- 

 colysis of guinea pig brain slices. Glucose was present in all, and 

 pyruvate or glutamate was added as indicated. (From Weil- 

 Malherbe, 1938.) 



to be relatively sensitive to maleate, a depression of the operation of the 

 cycle leading to accelerated glycolysis is suggested. However, the effects 

 of various substrates on the response of the brain slices to maleate are 

 puzzling (Fig. 2-2). In the presence of pyruvate, for example, there is 

 relatively little inhibition of respiration (10%) by 20 mM maleate, and 



