LIVER AND ANIMO ACID LEVELS IN BLOOD 7c 
tissues. Here, we have used the eviscerated surviving rat with the liver left func- 
tionally in situ supplied by the hepatic artery as an alternative to an isolated liver 
perfusion study. Figs. 2-5 give a more complete hour-to-hour picture of the course 
of oxidation of L-[U-4C]phenylalanine and of pr-[2-4C|methionine. These results 
are typical of those also obtained with the essential amino acids histidine, lysine, 
arginine, threonine and tryptophane, in which oxidation by the liver is most extensive 
within the first few hours. Figs. 6 and 7 compare the oxidation of pL-[{1-!4C|leucine 
by the liver with that by the non-hepatic tissues. It is at once apparent that in 
contrast to the first group of essential amino acids, leucine is as extensively oxidized 
to 4#CO, by the non-hepatic tissues as by the liver. As Table I reveals, isoleucine and 
valine are similarly as extensively metabolized by the non-hepatic tissues as by the 
liver. 
The relatively low oxidation of L-[U-'C]leucine by both the liver and non-hepatic 
tissues is reflected in the unusually high incorporation of L-leucine into both liver and 
plasma proteins which we have described recently with GREEN’. 




50 50 
40 ISOLATED 40 
PERFUSED O—O 
% DOSE !4¢ SO LIVER CUMULATIVE 
AS COp NON-HEPATIC % DOSE !4¢ ISOLATED 
PER HOUR TISSUES @—® AS CO, PERFUSED Q-O 
2 20 LIVER 
NON-HEPATIC oe 
TISSUES 

lo 
ce) 
I ABs Sey xh 2G 
HOURS HOURS 
Fig. 6 Fig. 7 
Fig. 6-7. Oxidation of pL-[!4Cjleucine by the liver compared with non-hepatic tissues. Rat liver 
perfusion (RLP 547). Fed Sprague-Dawley male (weight, 350 g) as liver donor. Liver weight, 
9.3} 17.5 mg DL-[1-!Cjleucine (3.3 wC) plus 500 mg glucose added to the perfusion blood 
(83 ml) at the outset of the experiment. Duration of experiment, 5 h. Eviscerated surviving rat 
(EV R-LE-16), male, Sprague-Dawley (weight, 245 g), eviscerated under ether anesthesia. 3.5 mg 
(3.3 wC) DL-[1-l4C]leucine plus 31.6 mg L-leucine injected intravenously in 2.2 ml of saline at the 
outset of the experiment. Duration of experiment, 5 h. 



60 
60 
50 50 
\4¢ LIVER IN| O—O CUMULATIVE liver in O-O 
AS Cp ae % DOSE I4¢ LIVER out @-@® 
PER HOUR a6 LIVER OUT @—® AS CO, - 
20 20 
10 10 
0 1 
Tees) 34s ie} ie LSS aES 
HOURS HOURS 
Fig. 8 Fig. 9 
Fig. 8—g. Oxidation of L-/44C)alanine in the eviscerated rat. Eviscerated surviving rat (EV R-AL-3)? 
male, Wistar (weight, 287 g); dose of 38.25 mg L-[ U-!4Cjalanine, 0.05 mg L-/ U-!4Cjalanine (5C) 
plus 22 mg pi-alanine in a volume of 2 ml of saline given intravenously at the outset of experi- 
ment. Duration of experiment, 5 h. Eviscerated surviving rat (EVR-5), normal male, Sprague- 
Dawley (weight, 351 g), liver left functioning supplied with hepatic artery; dose identical with 
EVR-AL-3, given at outset of experiment. Duration of experiment, 5 h. Liver weight, 8.6 g. 
References p. 721 
