560 A. LAJTHA 
conditions the glycine influx coefficient could be reduced without a change in the 
efflux coefficient in ascites*? and that in galactose transport in E. coli34 the exit 
process was found to be to some extent independent of the entry process in that 
efflux could be increased or decreased without corresponding changes in influx. 
Further studies are necessary to establish the relationship between cerebral influx 
and efflux of the amino acids. 
The differences in behavior between the individual amino acids should caution us 
not to generalize from observations made on a single compound. 
TABLE III 
THE EFFLUX OF L-AMINO ACIDS FROM RAT BRAIN 

Minutes afier Increase over control wmoles/roo g fresh brain 
administration 


Leucine Phenylalanine Lysine 
5 40 93 33 
20 15 93 FE 
45 2.3 30 72 
60 7363} 20 69 
120 fo) 5.2 54 
180 oO 39 
240 28 

2 wmoles of the amino acid were injected in 0.02 ml 0.9% saline 
subarachnoidally into young male rats. 
EFFLUX OF AMINO ACIDS FROM THE BRAIN 
Efflux of the amino acids from the brain when plasma levels are not elevated was 
studied after the intracerebral administration of 2 wmoles of an amino acid?*, With 
L-amino acids (Table III), maximal levels were reached at various times after 
administration, and the time to decrease to the physiological level was different for 
each of the amino acids studied. 
TABLE IV 
THE EFFLUX OF D-AMINO ACIDS FROM RAT BRAIN 

Minutes after pmoles/roo g fresh brain 
administration 


Leucine Phenylalanine Lysine 
5 59 71 66 
20 47 59 84 
45 18 38 78 
60 12 20 74 
120 1.6 4-9 63 
180 0.7 49 
240 43 

2 umoles of the amino acid in 0.02 ml 0.9% saline were injected 
subarachnoidally into young male rats. 
References p. 563 
