Insulin and the In Vitro Protein Synthesis of Liver and Skeletal Muscle Ribosomes in Experimental Acute Uraemia

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Abstract
Tissue dependent alteration of liver and muscle protein synthesis was previously observed in acute uremia, when intracellular amino acids were used as substrate. Since protein synthesis depends also on substrate availability, it was of interest to investigate the role of isolated liver and skeletal muscle ribosomes of nephrectomized rats and their susceptibility to in vivo insulin stimulation. Under marked uremic conditions, no difference was demonstrated between controls and uremic animals; after insulin administration and in the presence of endogenous messenger both liver and muscle ribosomes showed an enhancement of [3H]-phenylalanine incorporation of 20 and 54%, respectively, in controls, and of 32 and 45% respectively in uremic rats. This study may rule out the influence of acute uremia on protein synthesis capacity of isolated ribosomes and emphasize the importance of intracellular amino acid availability in altered protein synthesis.