Substrate regulation of the glucose transport system in rat skeletal muscle. Characterization and kinetic analysis in isolated soleus muscle and skeletal muscle cells in culture.
A self-regulatory mechanism of the glucose transport in rat skeletal muscle cells is described. In isolated rat soleus muscles and rat skeletal myocytes and myotubes in culture, pre-exposure to varying glucose concentrations modulated the rate of 2-deoxyglucose uptake. Maximal uptake was observed at glucose concentrations below 3 mM. Between 2.5 and 4.0 mM glucose it was reduced by 25-35%; further elevation of the glucose concentration resulted in a gradual decrease of the transport rate by approximately 2% for each millimolar glucose. The effect of glucose was time-dependent and fully reversible. Insulin rapidly increased the 2-deoxyglucose uptake in the soleus muscle; however, the insulin effect depended on the glucose concentration of the preincubation. Insulin was totally ineffective in muscles pre-exposed to 1.0-3.0 mM glucose, whereas its stimulatory action increased with increasing glucose concentrations above 4 mM. The effect of low glucose and insulin were not additive, and the maximal 2-deoxyglucose uptake rates induced by both conditions were of identical magnitude. It is postulated that glucose may "up- and down-regulate" its transport by affecting the number of active glucose transporters in the plasma membrane, and that insulin exerts its stimulatory effect only when the extracellular glucose reaches a threshold concentration.
D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D003847:Deoxyglucose / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D000621:Aminoisobutyric Acids; D009004:Monosaccharide Transport Proteins; C100049:2-aminoisobutyric acid; D003847:Deoxyglucose