Insulin-like action of catecholamines and Ca 2+ to stimulate glucose transport and GLUT4 translocation in perfused rat heart

Abstract

The uptake of 2-deoxyglucose by perfused rat hearts was compared to the distribution of the insulin-regulatable glucose transporter (GLUT4) in membrane preparations from the same hearts. The hearts were treated with the α-adrenergic combination of epinephrine + propranolol, the β-adrenergic agonist isoproterenol, high (8 mM) Ca 2+ concentrations, insulin and the alpha adrenergic combination or insulin alone. Epinephrine (1 μM) + propranolol (10 μM), isoproterenol (10 μM), high Ca 2+, insulin (1 μM) + epinephrine (1 μM) + propranolol (10 μM) and insulin (1 μM) each led to an increase in 2-deoxyglucose uptake and a shift in the recovery of the GLUT4 from a high-speed pellet membrane fraction (putatively intracellular) to a low-speed pellet membrane fraction (putatively sarcolemmal). There were significant correlations ( r = −0.673, P < 0.001) between the stimulation of 2-deoxyglucose uptake and the loss of GLUT4 from the intracellular membrane fraction, or the increase in the sarcolemmal fraction. The data provide evidence that the GLUT4 is translocated by agents that stimulate glucose transport in heart, and therefore this mechanism is not restricted to insulin.