Abatrad. The rate of incorporation of leucine into hepatic proteins in liver slices from 42 patients was studied. Zero order kinetics for the incorporation of leucine i n relation to the incubation time and to the amount of incubated roteins were obtained, provided that the medium containex a complete amino acid mixture with a concentration 4 timee that of normal human serum.h u h space and water content of the preparation were of the m e magnitude 88 reported for rat liver. The presence of fructoee (5.5 mM) in the medium caueed an inhibition of the rate of incorporation of leucine into pro-teins. hadin the medium, however, stimulated tho inration rate.h u m i n g that the rate of incorporation :runcine into he tic proteina is representative of protein synthesis, the half% of liver proteins can be calculated to be 35 days for subjects below 60 yeare of age. For those who were older than 60yeara. the protein turnover rate waa approximately 30% higher. Key d.-Hman liver, protein synthesis, protein turnover, human liver, lq-leucine.

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Extrahepatic cholesbsis in man is known to be associated with high phosphoglyceride and cholesterol concentrations in serum. Moreover, an abnormal lipoprotein, often referred to as lipoprotein-X (LP-X), appears in serum in cases of extrahepatic cholesbsis.The purpose of this study was to determine the rate of incorporation of precursors into hepatic lipids and proteina in uitro and to compare these changes with the lipoproteins in plasma in patients with extrahepatic cholestasis. The rate of incorporation of glycerol into triglycerides and into different classes of phosphoglycerides was determined. The rate of incorporation of leucine into proteins was also determined in liver slices from 16 patients with extrahepatic cholestasis and compared with controls. In cholestatic liver tissue, the rate of incorporation of glycerol into choline phosphoglycerides and into ethanolamine phosphoglycerides was significantly increased. The rate of incorporation of leucine into hepatic proteins was also increaaed significantly in these patients. The results suggest that the changed metabolism of phospholipids and protein in liver tissue in cholestatic conditions may contribute to the changes in the serum lipoprotein pattern.

The rate of incorporation Of leucine into hepatio roteins in liver slices from 42 patients was studied. Zero order L e t i c s for the incorporation of leucine in relation to the incubation time and to the amount of incubated proteins were obtained, provided that the medium oontained a complete amino acid mixture with a concentration 4 times that of normal human Berum. -Inulin space and water content of the reparation were of the same magnitude as reported for rat Ever. The presence of fructose (5.6 mM) in the medium caused an inhibition of the rate of incorporation of leuclne into pro-teins. Insulin in the medium, however, etimulated the incor ration rate.h u m i n g that the rate of incorporation of Ecine into hepatio protern is representative of protein synthesis, the half-life of liver proteins can be calculated to be 35days for subjects below 60yeara of age. For those who were older than 60yeara, the protein turnover rate waa approximately 30% higher.Key m d s : Human liver, protein synthesis, protein turnover, human liver, l*Cleucine.