Role of calcium in serum-stimulation of hexose transport in muscle cells.
Serum stimulates glucose uptake into several cells in culture. In intact muscle, an increase in cytosolic free Ca2+ has been proposed to mediate the activation of glucose uptake by hormones and other stimuli [Cell Calcium (1980) 1, 311-325]. We report that hexose (2-deoxy-D-glucose) uptake into L6 muscle cells in culture is enhanced several-fold by fetal calf serum. The increase in uptake is due to stimulation of transmembrane transport, since serum also stimulated uptake of the non-metabolizable hexose 3-O-methyl-D-glucose. The role of Ca2+ in this stimulation was assessed: (i) stimulation of transport by serum was independent of the presence of extracellular Ca2+ during the incubation with serum; (ii) the intracellular levels of free Ca2+, measured by the fluorescence of the novel Ca-indicator quin-2, were identical in serum-stimulated and control cells. It is concluded that hexose transport can increase in muscle cells without concomitant changes in cytoplasmic free Ca2+.
D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000097:blood / Q000502:physiology*; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D051381:Rats
D006601:Hexoses; D003513:Cycloheximide; D003847:Deoxyglucose; D002118:Calcium