AMINO ACID TRANSPORT IN EHRLICH CELLS 543 
there are certain basic groups at the cell surface, which are indispensable for the 
full function of the transport mechanism but which do not directly combine with 
the attaching group of the substrate amino acid. 
A similar much weaker effect on glycine influx is exerted by short-term (2 min) 
increase of the K+ ions (Fig. 6). This effect is much smaller than that observed pre- 
14 
| c| Glycine 
11) 
Relative influx 

50 100 150 
Extracellular [Na*] Mequiv./| 
Fig. 7. Glycine influx and extracellular Nat concentration. K* concentration is kept constant 
at 6 mequiv./l. The decrease of Na+ ions is compensated for by choline ions’. (Fig. reproduced by 
permission of Springer-Verlag). 
viously by CHRISTENSEN in long-term experiments on the steady-state distribution 
of glycine!®. The inhibitory effect of potassium on the flux, however, seems to be 
only apparent and rather due to the concomitant decrease in extracellular sodium. 
Accordingly an increase of potassium scarcely inhibits the glycine influx if by the 
TABLE If 
INTRACELLULAR LEVELS OF NAt AND Kt AND 
GLYCINE INFLUX 
Extracellular concentrations are the same in 
all experiments, 7.e. corresponding to Krebs- 
bicarbonate—Ringer solution. 


Intracellular 
== : Relative 
[K+] glycine influx 
—————E (ml/g 2 min) 
(mequiv.|l) 

[Na*] 

61 168 9-7 
167 74 9.8 

use of choline the Na+ concentration of the medium is kept constant (Fig. 6). On 
the other hand the glycine influx diminishes when the extracellular sodium is re- 
duced below a value of approx. 90 mequiv./l, even at constant K* concentration 
(Fig. 7). Provided choline is as indifferent to transport systems and permeability as 
References p. 544 
