DECREASE IN MUSCLE GLUCOSE TRANSPORTER NUMBER IN CHRONIC PHYSICAL INACTIVITY IN RATS

In this study, whole body insulin action on glucose uptake and muscle glucose transporter number of rats subjected to 14 days of physical inactivity conditions was examined. Unlike other suspension and denervation models of muscle disuse, this physical inactivity model allows voluntary contractile activity with minimal stress. Minimal depression of body weight gain and significant depression of gastrocnemius muscle growth were observed compared with that of control rats after 14 days of physical inactivity. The whole body insulin sensitivity and responsiveness were determined by the euglycemic clamp technique, with 1.4, 3.6, and 14 mU insulin.kg-1.min-1 perfusion and 2-deoxy-D-[H-3]glucose incorporation. The rates of glucose disposal were the same in the restrained rats as in the controls with the 1.4 and 3.6 mU insulin perfusion; however, glucose disposal significantly decreased with 14 mU insulin perfusion. 2-Deoxy-D-[H-3]glucose uptake into the gastrocnemius muscle was higher in the control rats than in the physically inactive rats. Glucose transporters in the gastrocnemius and quadriceps muscles, measured by means of the D-glucose-inhibitable cytochalasin B binding assay, were significantly decreased in number in the physically inactive rats. These findings suggest that the decrease in whole body glucose uptake might in part be explained by the decreases in the total glucose transporter number in muscles.