FACTORS AFFECTING METABOLISM itl vitro 



131 



later transferred to salines containing an additional 90 mM KCl, 

 breakdown of phosphocreatine occurred in two steps, the first and 

 second steps each occupying some 20 sec, between each was a 

 stable period of 30 sec (Fig. 16). Whether curves a and b represent 

 the same processes carried out at different rates can only be con- 

 jectured. The time course of the overall change was the same in 

 both experiments. Changes of this type are not likely to permit of 

 simple interpretation and such situations require further analysis. 

 Conditions leading to decreased levels of phosphocreatine were 

 noted to decrease the rate of incorporation of radioactive phosphate 

 into compounds such as the phospholipids. Analogous effects 

 have been found with increased concentrations of potassium salts 

 (Table 20). Thus, potassium salts at 124-0 mM markedly de- 

 creased the amount of radioactive phosphate incorporated into 

 phospholipids, phosphoprotein and nucleic acids of cerebral 

 slices. This effect was obtained to a lesser degree with potassium 



Table 20. — Effect of Potassium Salts upon the Incorporation of 



Radioactive Phosphate into Phospholipids, Phosphoproteins and 



Nucleic Acids of Cerebral Cortical Slices 



Data from Findlay et al. (1954) (Expts. 1 and 2) and Tsukada et al. (1958) 

 (Expt. 3). 



