Tissue glycogen fractions of the hypothermic rat, hamster, and turtle

Hypothermia in fasted rats caused reduction of both glycogen fractions in liver and heart but did not affect skeletal muscle. Forced respiration during hypothermia prevented the reduction of residual glycogen in heart, but did not otherwise alter the tissue glycogen response to hypothermia. Bilateral adrenalectomy did not prevent the loss in hypothermia of either glycogen fraction from heart or liver. Prevention of shivering by curare during hypothermia failed to maintain control levels of liver or heart glycogen fractions. Incorporation of intraperitoneal glucose-C14 into tissue glycogen of hypothermic rats was increased in soluble and residual fractions of heart, but not in liver or muscle. It was concluded that disappearance of hepatic glycogen in hypothermia may be due to an accelerated glucose utilization by myocardium, and furthermore, that soluble glycogen is the more labile fraction. The same tissues of hamsters and turtles showed no changes in either glycogen fraction due to hypothermia.