Oxidation of leucine by rat skeletal muscle
Odessey, R.; Goldberg, A.L.
American Journal of Physiology 223(6): 1376-1383
1972
ISSN/ISBN: 0002-9513 PMID: 4641630 Document Number: 53080
In the isolated rat diaphragm, 14CO2 was produced from L-leucine-1-14C at 86% of the rate of its incorporation into protein. Experiments with L-leucine-U-14C indicate complete oxidation of leucine under these conditions. 14CO2 production from leucine-1-14C was inhibited slightly by glucose (15%) but not by acetate, pyruvate, beta -hydroxybutyrate or palmitate. Amino acids at plasma concentrations inhibited 14CO2 production by from 30 to 40% without affecting protein synthesis. Cycloheximide blocked incorporation into protein but stimulated 14CO2 production, whereas cyanide and iodoacetate inhibited both processes. Addition of ouabain or the removal of Na+ from the incubation medium inhibited incorporation into protein but not oxidation. Appreciable oxidation of leucine also occurred in the dark soleus and the pale extensor digitorum longus muscles. The diaphragm catabolized leucine at rates similar to liver slices but less actively than epidydimal fat pad or kidney and brain slices. Since skeletal muscle accounts for over 40% of the body mass, muscle is probably the major site of leucine catabolism in the animal.