Carbohydrate Metabolism During Fasting and Hibernation in the Ground Squirrel

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Abstract
Biochemical levels of glycogen, lactate and pyruvate determined in liver, skeletal muscle and cardiac muscle of control, fasting and hibernating groups of ground squirrels were compared. During fasting liver glycogen increased, as compared to the control, apparently as a result of glycolysis in both skeletal and cardiac muscle. The lactate-pyruvate ratio in both types of muscle greatly favored lactate. Therefore, it is possible that the formation of a ‘lactate pool’ by muscle supplies the glycogenetic needs of the liver at this time. In hibernation both liver and cardiac muscle showed increases in glycogen over control values. Possibly, this may subsequently serve as a source of energy for arousal. Lactate and pyruvate during hibernation decreased in all tissues studied due to a low metabolic rate slowing the process of glycolysis. However, the ratio between the two compounds remained within the control range. The data suggest that the mechanism of carbohydrate metabolism during fasting differs from that during hibernation.