56 The Chemistry of the Injured Cell 



which may be prevented by the addition of oxidisable substrate. 

 Similarly, in isolated mitochondria damaged by contact with high 

 concentrations of calcium, loss of oxidative phosphorylation may 

 be prevented by the addition of ATP and of DPN. 



It is of interest that although the addition of glucose will allow 

 oxidative phosphorylation to proceed in liver cells isolated from 

 their blood supply, even in the absence of oxygen, the level of ATP 

 in the cells falls progressively unless oxygen too is supplied. This 

 observation confirms the inability of glycolysis alone to maintain 

 energy generation and ATP synthesis. Another interesting fact is 

 that the level of -SH groups in the cell (chiefly glutathione) falls 

 rapidly in an isolated liver supplied with oxygen and less rapidly 

 under anaerobic conditions. The nature of this phenomenon is 

 obscure. 



Isolated livers supplied with glucose or with oxygen plus an 

 oxidisable substrate maintain metabolic activity for several hours. 

 Eventually, however, they develop the failures described above. 

 This subsequent collapse reveals further weak links in survival. 

 Thus the loss of coenzymes at this stage is partly due to a shortage 

 of their precursors, e.g., adenosine and nicotinamide. Another and 

 probably very important factor influencing survival at this stage 

 is the level of liver glycogen, this substance probably representing 

 the most readily available substrate. The superiority of glycogen 

 over glucose as a means of increasing survival is probably due to the 

 fact that utilisation of glucose requires hexokinase and ATP both 

 of which may be deficient in the cell isolated from its blood supply. 

 The accumulation of intracellular calcium (due to disturbances 

 of electrolyte metabolism) cannot be the cause of eventual de- 

 terioration of respiratory activity (calcium is a respiratory poison), 

 since calcium accumulation may be prevented with the aid of 

 promethazine HC1 (phenergan) without affecting the respiratory 

 decline. The synthesis of complex molecules is amongst the last of 

 the cell's reactions to be lost. They fail eventually for lack of energy 

 due to loss of ATP synthesis. 



It can be seen that primary causes of cell death after loss of 

 blood supply are associated with disturbances of the reactions con- 



