DANIELLI 



and phosphorylative oxidation are not immediately involved. Phlorizin, phloretin 

 and phloretin phosphate are active, and are alkaline phosphatase inhibitors, suggest- 

 ing that alkaline phosphatase is concerned. Phloretin phosphate is colloidal, and 

 inhibits mainly exit of glucose from the red cell. 



In the case of sodium and potassium movements it is known that glycolysis, not 

 respiration, supplies the energy. But in the case of the (nucleated) red cells of the hen, 

 Maizels (1954) has shown that respiration provides the energy for active transport. 

 If the respiration of hen red cells is poisoned, glycolysis continues but is unable to 



Table II 



The action of enzyme poisons upon penetration into human red cells 



actuate active transport. This suggests that some form of coupling is necessary 

 between the energy-yielding process and the mechanism of transport. The fact that 

 glucose as a source of energy may be replaced by acetylcholine, and that the trans- 

 port mechanism may be poisoned with eserine, no matter what source of energy is 

 used, suggests that cholinesterase is concerned in the mechanism of transport 

 (Hollander and Grieg, 1950). The failure of phlorizin, phloretin and phloretin 

 phosphate to inhibit active transport of K+ and Na+ appears to exclude alkaline 

 phosphatase. 



The general conclusion which emerges from these studies is that enzyme-like 

 membrane components appear to be active both in facilitated diffusion and active 

 transport. The detailed examination of the composition of red cell membranes should 

 clearly be pursued. Reviews bearing on this problem have been published by Brown 

 (1952) on plant cells and by Rosenberg and Wilbrandt (1952) on animal cells. 



