SUITABILITY OF 2-DEOXYGLUCOSE FOR IN-VITRO MEASUREMENT OF GLUCOSE-TRANSPORT ACTIVITY IN SKELETAL-MUSCLE

The purpose of this study was to evaluate the suitability of the gluco se analogue 2-deoxyglucose (2-DG) for measurement of glucose transport activity in rat skeletal muscles in vitro when transport rates are hi gh. The goal was to determine whether glucose phosphorylation rather t han transport becomes limiting under experimental conditions normally employed in muscle incubation experiments. The rate of 2-DG uptake ass ayed in the presence of 8 mM 2-DG and a maximally effective concentrat ion of insulin remained linear for greater than or equal to 60 min in the split soleus and 120 min in the epitrochlearis. Hexokinase activit y assayed in skeletal muscle homogenates was not inhibited appreciably by 2-deoxyglucose 6-phosphate (2-DG-6P) concentrations in the range o f those achieved intracellularly during the linear phase of 2-DG uptak e (i.e., 2-DG-6-P below similar to 30 mM). During this linear phase of 2-DG uptake, total intracellularly 2-DG concentrations did not exceed 30 mM. The combined effects of contractions plus a maximally effectiv e concentration of insulin on glucose transport activity measured at a near-saturating concentration of 2-DG were additive in the epitrochle aris and the soleus. Our results indicate that, under the conditions e mployed in our isolated muscle preparations, 2-DG uptake accurately re flects glucose transport activity and that 2-DG is the most appropriat e glucose analogue for measurement of glucose transport activity when transport rates are high.