Enhanced muscle protein degradation and amino acid release from the hemicorpus of acutely uremic rats.

Protein synthesis and degradation and net uptake and release of amino acids and minerals were investigated in the perfused hemicorpus of acutely uremic and control Sprague-Dawley rats. Rats underwent bilateral nephrectomy or sham surgery and were studied 30 hr after surgery. The uremic rats displayed greater urea N appearance (net urea generation), lower plasma and muscle concentrations of most amino acids, and increased muscle protein degradation as compared to control rats. Muscle protein synthesis was slightly but not significantly decreased in the uremic animals. There was greater net release of phenylalanine, tyrosine, alanine, total nonessential amino acids, total amino acids, potassium and phosphorus from the perfused hemicorpus of uremic rats and greater release of citrulline from sham rats. Muscle ATP, creatine phosphate, cyclic-AMP, and activities of cathepsin B1, cathepsin D, and alkaline protease were not different in the uremic and sham rats. These data provide evidence that acutely uremic rats sustain increased muscle protein wasting which is due to enhanced protein degradation. The increased protein degradation does not appear to be due to enhanced activities of muscle cathepsin B1, cathepsin D or alkaline protease.