Glycogen depletion - repletion Characteristics of Different Types of Skeletal Muscle Fiber in Streptozotocin - diabetic Rats

Koo, Hwan Mo; Kim, Sae Dong; Ihn, Joo Chul

Abstract

In this study, the glycogen depletion and repletion of 4 hind limb skeletal muscles which are composed of different type of muscle fibers were investigated in the streptozotocin induced diabetic rats. At sixth day after intraperitoneal injection of streptozotocin (65mg/kg, BW), the plasma insulin level was decreased to 28.2 ±4.16u U/ml comparing with the level of 49.3 ±9.41 in control rats, And it showed approximatly 300% increment of the level of blood glucose concentration in the sedentary diabetic rats. The soleus (slow oxidative), rad gastrocnemius (fast oxydtive glycolytic), extensor digitorum longus (fast oxidative glycolytic and fast glycolytic mixed), and white gastrocnemius (fast gltycolytic) were subjected in this study. The decreased amount of glycogen in the muscles by 3 minutes treadmill running in disbetic rats was larger than that of control rats. The largest amount of depletion was observed in the soleus in diabetic rats. The repleted amount of muscle glycogen was measured at 2 hours after glucose ingestion (25% glucose sol., 2ml/10gm BW). In the control rats, the highest amount of glycogen was repleted in the soleus, but lowest in white gastrocnemius. The repleted amount of glycogen in soleus, red gastrocnemius, and extensor digitorum longus was lower in the muscles of diabetic rats than in control rats, but no difference was observed in white gastroenemius muscles. These data suggest that glycogen synthetic activities of all of muscles except the muscles which are composed of fast glycolytic fiber, were stimulated by insulin.