Carbohydrate Metabolism of Hypophysectomized Dogs as Studied With Radioactive Glucose

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Abstract
Minute amounts of uniformly labeled C14 glucose were administered intravenously to unanesthetized normal and hypophysectomized dogs, in the postabsorptive state, as an initial priming injection, followed by a constant infusion. From the observed specific activity of the plasma glucose during the 60–180-minute period of the constant infusion, the following parameters of carbohydrate metabolism were determined: a) the size of the glucose pool, b) the glucose space and c) the rate of turnover of the glucose pool. The rate of total CO2 production was also determined. The rate of total CO2 production, per square meter of body surface area, was found to be less in the hypophysectomized dog than in the normal one. The glucose pool, per kilogram body weight, was found to be smaller in the hypophysectomized dog than in the normal one. The glucose space, expressed as percentage of body weight, was found to be similar in the two types of animals. The rate of turnover of the glucose pool in the hypophysectomized dog, presented as grams glucose per square meter of body surface area per hour, was found to be less in the hypophysectomized dog than in the normal one. The low rate of glucose uptake by the tissues which was observed to prevail in the hypophysectomized dog is believed to reflect an adjustment in the secretion of insulin to conform to the limited availability of endogenous glucose which results from the removal of the pituitary gland.