Metabolism of branched-chain amino acids in dogs with Escherichia coli endotoxin shock.

The arterial-femoral venous difference of phenylalanine concentration is proportional to net proteolysis in the leg. In ten fasting dogs receiving Escherichia coli endotoxin (2 mg/kg) intravenously, the mean systolic blood pressure decreased from 141.1 +/- 25 to 71.5 +/- 17 mm Hg. The absolute net release from the leg of valine, isoleucine, and leucine and their net release relative to net proteolysis (arterial-femoral venous difference in concentration of each branched-chain amino acid relative to that of phenylalanine) were decreased, indicating increased transamination of these amino acids in skeletal muscle. However, the net release of the branched-chain alpha-keto acids formed by transamination, relative to net proteolysis (arterial-venous difference in concentration of each alpha-keto acid relative to that of phenylalanine), was not increased. The findings indicate that in dogs with E. coli endotoxin shock, there is increased oxidative decarboxylation in muscle of the alpha-keto acids derived from valine, isoleucine, and leucine.