UPTAKé OF TYROSINE BY BRAIN 549 
2.00 

1.80 
top) 
fo) 
So 
fee) 
oO 
S 
a 
oO 
O— 09-C0p 
TISSUE CONCENTRATION (yg /gm ) 
MEDIUM CONCENTRATION (yg /ml ) 
8 
oS 
5 
oO 
©—* 0),- C0, (BOILED SLICES) 

0 20 40 60 80 100 120 140 
MINUTES 
Fig. 4. Uptake of L-tyrosine by brain slices. 
of the uptake of tyrosine under anaerobic conditions and the uptake by boiled slices 
made it apparent that tyrosine uptake can be divided into two components, a con- 
centrative component, dependent on aerobic metabolism, and a non-concentrative 
component, probably involving diffusion. 
When glucose or other hexoses (Table IV) were added to the buffer the uptake 
TABLE IV 
EFFECT OF VARIOUS CARBOHYDRATES ON L-TYROSINE UPTAKE 
BY BRAIN SLICES 
Figures in parentheses indicate number of incubations. Slices 
incubated for 60 min in 10 ml of Krebs—Ringer—bicarbonate 
buffer containing L-tyrosine (1 x 10% M) and the indicated 
carbohydrate (1 x 10°? M). 

Intracellular concn. (g/ml) 


Compound ae 
Medium concn. (g/ml) 
Control 2.73 - 0.28* (36) 
p-Glucose 4.63 + 0.39 (12) 
p-Galactose 3.59 + 0.34 (8) ‘ae 
p-Fructose 3.99 + 0.44 (8) ; i H. ( ) 
p-Mannose 4.71 + 0.44 (8) AN , 2 
p- Ribose 2.87 (2) 
2-Deoxyglucose 3.02 (4) 
p-Glucose-6-phosphate eyntsie (2) VW ao) ae 
Mannitol 2.95 (4) 7 
Sorbitol 2.93 (5) i 
Sucrose 2.91 (6) 
Maltose 3.10 (4) 
Lactose 2.84 (4) 


* Mean + standard deviation. 
References p. 553 
YA 
