Leucine and protein metabolism after bilateral nephrectomy in rats: the role of hepatic tissue

The aim of this study was to evaluate the effect of acute uremia on changes in leucine and protein metabolism in the whole body and in hepatic tissue. Acute renal insufficiency was induced by bilateral nephrectomy (BNX), Twen ty-four hours later, parameters of protein and amino acid metabolism were e valuated in the whole body using primed constant intravenous infusion of L- [1-C-14]leucine, and in isolated perfused liver (IPL) using alpha -keto[1-C -14]isocaproate. The control group consisted of sham-operated rats. BNX ind uced a marked decrease in proteolysis, protein synthesis, Ieucine oxidized fraction and Ieucine clearance. The decrease in protein synthesis was highe r than in proteolysis. A significant drop in protein synthesis was observed in muscle, gut, heart and spleen. The study with IPL in BNX animals showed decreased oxidation of ketoisocaproic acid and higher concentrations of th e branched-chain amino acids (BCAA) leucine, isoleucine and valine in perfu sion solution. We conclude that the cause of rapid depletion of body protei ns after BNX is a greater decrease in protein synthesis than in proteolysis associated with an increase in leucine oxidized fraction. The data obtaine d in the IPL model indicate that BNX causes metabolic changes that enable r esynthesis of BCAA from corresponding branched-chain keto acids in liver.