Metabolic Studies in Human Skeletal Muscle Tissue

Abstract

An in vitro preparation of human skeletal muscle tissue aimed to be a model for clinical metabolic studies was functionally and structurally characterized. Muscle fibres from biopsy specimens obtained at surgical operations were teased away and collected in incubation vessels for the following determinations: exchangeable water content, extracellular space, potassium content, incorporation rate of labeled leucine into proteins, uptake of labeled cycloleucine, α-aminoisobutyric acid (AIB), and 3-O-methyl-glucose into the intracellular space, and the incorporation rate of glucose into various metabolites. After various times of incubation, muscle fibre samples were also taken for light and electron microscopy.During the incubation of the muscle fibres a transient intracellular oedema was demonstrated by electron microscopy and by determination of the exchangeable water content. The restitution of this oedema was associated with an increasing intracellular potassium concentration. Active transport of leucine, cycloleucine and AIB showing competitive inhibition was registered. The incorporation of labeled leucine into proteins was linear during 4 h of incubation and optimal stimulation of this incorporation was demonstrated in the presence of a complete amino acids mixture at a concentration corresponding to 10 times the normal plasma concentration in man. Insulin stimulated the incorporation rate of glucose-carbon into all metabolites and ouabain stimulated its incorporation into glycogen. Monoiodoacetate inhibited the incorporation of glucose into all metabolites.The teased human skeletal muscle tissue seems to be a useful model for clinical studies of human skeletal muscle metabolism. Several regulatory systems, which arefunctional in the intact and the cut rat diaphragm were present and functional in these isolated human fibres.