Cyclic changes in carbohydrate concentrations during hibernation in the arctic ground squirrel.

GALSTER, WILLIAM A., AND PETER MORRISON. Cyclic changes in carbohydrate concentrations during hibernation in the arctic ground squirrel. Am. J. Physiol. 218(4): 1228-1232. 1970.-Blood samples from right ventricular cannulas and tissues were collected from arctic ground squirrels during summer and winter. Average plasma glucose (mg/ml) and tissue glycogen (mg/g) values from ‘Cunexcited” fasted ground squirrels in summer (plasma, 0.85; liver, 17.8; thigh muscle, 4.5; kidney, 0.2; heart, 0.8; and brown fat, 0.1) were not significantly different from values in nonhibernating squirrels during winter. Results in hibernating squirrels were correlated with the time in hibernation since the previous arousal. In the first one-fifth of each hibernation period, average values for liver glycogen did not change, but values in the other tissues and plasma glucose were doubled. Plasma glucose, and glycogen in liver and thigh muscle declined steadily during each hibernation period, but glycogen concentrations in kidney, brown fat, and heart did not change. Values at the end of the hibernation period approached 0.5 mg/ml (plasma), 5.0 mg/g (liver) and 4.0 mg/g (thigh muscle). These tissues appear to represent a glucose “pool,” one-half of which is utilized during each of the hibernation periods and restored during each active period. It is suggested that these declines, and particularly that in plasma glucose, may directly initiate arousal in this species.