110 



FACTORS AFFECTING METABOLISM in Vttro 



inorganic phosphate (some 4-5 jLtmoles/ml.) permitting a relatively 

 low uptake of oxygen in vitro were similar to those found in vivo 

 during sleep or narcosis (Table 7). On the other hand concentra- 

 tions (7-lOju.moles/ml.) associated with high rates of oxygen 

 uptake in vitro are similar to those found in vivo in cerebral tissues 

 suffering from injury or in a state of convulsive activity (Table 7). 

 In vivo it is well known that narcosis or sleep reduces cerebral 

 oxygen consumption which is increased during increased activity 

 and parallelisms with changes in phosphates under these conditions 

 have already been pointed out (Chapter 2). 



Increase in oxygen uptake by dispersions in the presence of 

 increased quantities of inorganic phosphate also requires the 

 presence of a phosphate acceptor such as adenylic acid which is 

 presumably phosphorylated to adenosine triphosphate, the three 

 phosphates together forming a complete system. A similar system 

 is formed by inorganic phosphate, phosphocreatine and creatine. 



-75 13 



Applied potential 



Fig. 11. Relationships between levels of phosphocreatine and 

 inorganic phosphate, and the rate of oxygen uptake by slices of 

 guinea pig cerebral cortex. Slices were stimulated electrically as 

 described in the text. O = phosphocreatine; • = inorganic 

 phosphate; data from Heald (unpublished). + = increase in 

 oxygen uptake; data from Wollenberger (1955). 



