210 E. Racker and R. Wu 



Anaerobic conditions or the presence of 2 : 4-dinitrophenol 

 (DNP) resulted in a marked stimulation of lactic acid pro- 

 duction in ascites cells. Determination of the intracellular 

 content of phosphate and adenine nucleotides revealed that 

 pronounced fluctuation in inorganic phosphate (Pi) levels 

 occurred which were roughly proportional to the rate of 

 glycolysis. Similar changes in ADP levels were observed but 

 they were neither as striking nor as consistent as the Pi levels. 

 To explore the possibility of phosphate as a limiting factor of 

 glycolysis, the extracellular Pi concentration was raised, as 

 shown in Table IV. There was a marked stimulation of lactic 

 acid production when the Pi level in the suspension medium 

 was increased. Inclusion of adenosine monophosphate (AMP) 

 in the medium had no effect on glycolysis, although increments 

 of intracellular adenine nucleotides were noted under these 

 conditions. 



Table IV 

 Effect of extracellular Pi concentration on 



GLYCOLYTIC RATE 



Cells were incubated in air with glucose at 30 °C for 30 minutes. Results are 

 expressed as ti.moles/140 mg. protein. 



In view of these findings it was decided to investigate the 

 rate of phosphate entrance into the ascites cells. This was 

 done by measuring both intracellular Pi concentrations as 

 well as 22p distribution under various experimental conditions. 

 As illustrated in Table V, the transport of Pi into the cells is 

 dependent on a functional energy-yielding process such as 

 respiration or glycolysis. Respiration becomes ineffective for 

 Pi transport in the presence of DNP, a known uncoupler of 

 oxidative phosphorylation. Glycolysis-linked transport is 

 abolished on addition of iodoacetate. 



We arrived at the second conclusion: in ascites cells the 



