CLUES FROM ASSOCIATED EVENTS 



fluxes associated with the movements of the amino acids and sugars. 

 Ehrlich cells lose potassium ion and gain sodium ion as neutral amino 

 acids are accumulated (Christensen and Riggs, 1952). This exchange 

 appears to be meaningless as far as the preservation of clcctroneu- 

 trality is concerned, and should not be confused with migration of 

 inorganic ions necessarily set up when cationic or anionic amino 

 acids are transported (e.g., potassium ion uptake with glutamate). 

 The ability of the Ehrlich cell to accumulate neutral amino acids 

 has, in fact, been associated with their potassium-ion content, or 

 their ability to receive sodium ion in exchange for it ( RWs et al., 



J O \ DO 



1958). These alkali metal ion fluxes occurring when amino acids 

 are taken up are large enough to suggest that one or both of them 

 might supply the energy for the amino acid uptake, i.e., by driving 

 the carrier outward to make it more available for amino acid entry. 

 This suggestion might imply that energy is supplied directly to 

 alkali metal transport only, other transports then being satellite 

 transports. It is also significant that high sensitivity to alkali metal 

 distribution, both for amino acid and sugar transport, is not found 

 in human red blood cells but only where the transports are uphill. 

 The evaluation by Hempling and Hare (1961) of the flux augmenta- 

 tion on adding glycine, however, leaves the energy available from 

 the extra potassium-ion efflux alone somewhat short of that pre- 

 sumably required for glycine uptake. If we may also count the 

 energy of the accompanying sodium-ion entry, to drive an amino 

 acid carrier-complex inward, enough energy is available for the 

 task. A perhaps more likely explanation will be suggested later in 

 this chapter. 



Similar associations of sodium-ion migration with the intestinal 

 absorption of sugars and amino acids have also been observed and 

 have received an interpretation somewhat similar to that given above 

 (Csaky and Thale, 1960; Csaky, 1961; Crane et ah, 1961). In this 

 connection Csaky and associates (1961) and Crane and co-workers 

 (1961) have observed that ouabain, known as an inhibitor of alkali 

 metal transport, inhibits intestinal monosaccharide transport. 



The dimerizer theory of Stein (1961a) makes one molecule 

 of a solute the carrier for a second molecule. In this case, the kinetics 

 will be expected to show the increase of influx (well below satura- 

 tion) with the square of the solute concentration. In this connection, 

 Luzzatto and Leoncini (1961) have observed higher-order kinetics 

 for the cellular uptake of some sugars. 



79 



