ABRAHAM M. SHANES 



169 



fibers and used for comparison with a number of theoretical relations derived 

 for passive systems (20). The validity of such comparisons would be much 

 improved if metabolic processes could be eliminated as a complicating factor. 

 Moreover, the changes in tlux and E resultnig from metabolic inhibition can 

 serve as an important source of information concerning the nature of the link 

 between enzymatic reactions and ion distribution. 



As an example of the prospects of distinguishing the metabolic mechanism 

 which is predominantly involved, consider the effects on fluxes and E to be 

 expected from interruption of the four types of metabolic coupling mentioned 

 previously. These are summarized in Table 5. 



a) If potassium binding is dependent on metabolism, then inhibition will 

 increase the intracellular concentration of free potassium ions and therefore 

 the potassium outtlux and sodium influx. The fluxes in the opposite direction 

 will be altered as E declines with sodium and potassium interchange. 



Table 5. Changes in sodium and potassium fluxes and in resting potential, e, 

 anticipated from inhibition of different proposed metabolic 



mechanisms governing ion DISTRIBUTION IN RESTING NERVE 



( — ) represents a decrease, ( + ) an increase. 



b) A decrease in membrane selectivity would decrease E as sodium perme- 

 ability approaches that of potassium. Sodium outflux would rise as a result of 

 both permeability and potential changes; the increase in sodium influx, while 

 relatively less than the outflux, would still exceed the outflux, thereby causing a 

 rise in intracellular sodium. Potassium fluxes would alter only as expected from 

 the modification in E and from the requirement of electroneutrality of axo- 

 plasm and medium. 



c) A reduction in membrane potential would be as rapid as the interference 

 with metabolism and lead to changes in sodium and potassium fluxes corre- 

 sponding to alterations in E. 



d) Direct interference with potassium influx and sodium outflux resulting 

 from active transfer will decrease these flu.xes with or without an appreciable 

 change in E depending on the contribution of transport to the resting potential. 

 The flu.xes in the opposite direction will be affected by alteration in E. 



From table 5, it is evident that the differences are sufficient to permit a 



