The effect of starvation and total parenteral nutrition on skeletal muscle amino acid content and membrane potential difference in normal man.
Skeletal muscle intracellular amino acids and transmembrane potential difference (Em) were measured in hospitalized volunteers during starvation and refeeding with total parenteral nutrition (TPN). Healthy volunteers underwent extremity amino acid flux measurement, percutaneous skeletal muscle biopsy and determination of skeletal muscle Em after ten days of starvation (ST), and after a subsequent ten day period of TPN. ST produced a significant (p less than 0.05) decrease in plasma essential amino acids when compared with normal ambulatory volunteers. Subsequent administration of TPN produced a significant extremity uptake of all essential amino acids except for threonine and uptake of the nonessential amino acids taurine, glutamate, tyrosine and arginine. ST produced a significant reduction in skeletal muscle free intracellular glutamine and a significant increase in isoleucine and leucine. These changes in free intracellular amino acids were not reversed by administration of TPN. At the conclusion of ten days of ST and ten days of TPN, there was a significant reduction (p less than 0.05) in skeletal muscle Em. The results demonstrate that abnormalities of intracellular amino acid concentrations and reduction of muscle Em are not specific to stress conditions, but rather they can be present during both unstressed ST and intravenous nutritional repletion.
D000328:Adult; D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D009132:Muscles / Q000378:metabolism* / Q000502:physiology; D010289:Parenteral Nutrition, Total; D013217:Starvation / Q000378:metabolism* / Q000503:physiopathology
D000596:Amino Acids