238 



Van R. Potter and Hermann Niemeyer 



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20 DPNH OXIDATION WITH GLUCOSE AS A SUBSTRATE 

 _♦ ♦ ADDITION OF ORTHOPHOSPHATE (>jM) 



10 



20 10 20 30 

 TIME (MINUTES) 



10 



Fig. 4. Influence of phosphate concentration on the oxidation of 



DPNH by brain supernatant. The composition of the medium 



was as in Fig. 3, but DPN was replaced by DPNH. 



for the triose phosphates. Further studies on this phenomenon 

 were not carried out. 



Eifect of TPN 



It was observed that TPN inhibited glycolysis produced by 

 the 83 or S3 preparations from rat brain. The effect could be 

 shown on glucose disappearance, lactic acid production and 

 orthophosphate uptake. In general, the effect on glucose was 

 less reproducible and of less magnitude than that on lactate, 

 and sometimes an increased glucose uptake was observed. The 

 TPN effect depends on the pH of the medium, as illustrated 

 in Fig. 1. 



Addition of mitochondria — The addition of fresh mito- 

 chondria enhanced the inhibition produced by TPN. Usually 

 the inhibitory effect produced by the simultaneous addition of 

 TPN and mitochondria was greater than that produced by 

 each component separately (Table II). In the presence of 

 aged mitochondria the effect of TPN was also much greater 



