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Abstract
The rat appears to be unable to utilize glucose during hypothermia. The objective
of this study was to examine carbohydrate homeostasis during induction, hypothermia,
and rewarming phases. Groups of normothermic animals were euthanized to serve as time
controls for comparison. Hypothermia (15 degrees C) was produced by exposure to helox
(80% helium:20% oxygen) at 0 +/- 1 degree C. Hyperglycemia was noted during the induction
process (169 +/- 8 in control vs 326 +/- 49 mg/dl). Serum glucose increased further
during 4 hr of hypothermia, but following rewarming (Tre of 33 +/- 1 degrees C) was
reduced (153 +/- 16 mg/dl) significantly (P less than 0.05). Serum insulin was depressed
during hypothermic induction (from 48 +/- 4 in controls to 19 +/- 3 microU/ml in hypothermic
rats) and increased only slightly during the arousal process, remaining significantly
lower than in normothermic subjects. Initial hepatic, skeletal muscle, and cardiac
glycogen concentrations were reduced 34, 68, and 75%, respectively, during hypothermic
induction. While liver glycogen decreased further during 4 hr of hypothermia, skeletal
and cardiac stores increased markedly. During rewarming, hepatic glycogen was markedly
decreased, while skeletal and cardiac stores were maintained. These data suggest that
hyperglycemia in the hypothermic rat can be accounted for by glycogenolysis and hypoinsulinemia.
In addition, this study indicates repletion of skeletal and cardiac muscle glycogen
during maintained hypothermia and sparing of muscle glycogen during rewarming.