Infusion of a branched-chain amino acid-enriched solution and alpha-ketoisocaproic acid in septic rats: effects on nitrogen balance and skeletal muscle protein turnover

Sepsis was induced by cecal ligation and puncture in male Sprague-Dawley rats weighing approximately 70 g and the animals were intravenously infused with one of four isocaloric solutions: group I (N = 16), 8.5% dextrose solution; group II (N = 16), alpha-ketoisocaproic acid (KIA, 5.1 mg/ml) in 8.5% dextrose; group III (N = 16), FreAmine HBC (containing 45% branched-chain amino acids) in 2.5% dextrose; and group IV (N = 17), FreAmine HBC in 2.5% dextrose + KIA (5.1 mg/ml). Eighteen hr after induction of sepsis, extensor digitorum longus (EDL) and soleus (SOL) muscles were dissected with intact tendons and incubated for the study of protein synthesis and degradation, which were measured as incorporation of 14C-phenylalanine into protein and release of tyrosine into incubation medium, respectively. Urine was collected for determination of nitrogen balance. Nitrogen balance, which was equally negative in groups I and II, was significantly improved in groups III and IV and became equally positive in these groups. Protein synthesis and degradation rates in incubated EDL and SOL muscles were similar to those which we have reported previously in septic rats. Except for a higher synthetic rate in SOL in group II, no other differences in protein synthesis or degradation rates between the four experimental groups were found. Thus, the present study showed that infusion of a branched-chain amino acid-enriched solution improved nitrogen balance in septic rats. KIA alone or administered with the amino acid solution did not affect nitrogen balance.(ABSTRACT TRUNCATED AT 250 WORDS)