Abstract
It has been shown previously 1 that liver glycogen is mobilized in fasting adrenalectomized animals when they receive insulin, or, is formed less rapidly, when they receive glucose plus insulin. This result led to an investigation of the influence of small doses of epinephrine on the carbohydrate metabolism of normal rats. During glucose absorption, epinephrine in doses of 0.02 mg. per 100 gm. rat, produced the following effects, with great regularity. It increased heat production, decreased the rate of intestinal absorption, and caused glycosuria. On an average, 6% of the glucose absorbed during 4 hours was excreted in the urine. An equally constant result was increased glycogen formation in the liver, demonstrable not only after 4 hours, but also after 1, 2 and 3 hours of glucose absorption. For the 4 hour period a complete balance of the absorbed glucose has been made. A comparison with the balance sheet of control rats shows:
Per 100 parts of absorbed glucose, × parts are:
It will be noted that glycogen formation in the muscles and glucose oxidation are diminished, while glycogen deposition in the liver is increased. This indicates that the muscles are unable to dispose of part of the absorbed glucose. According to our present conception, the sugar which the muscles fail to utilize, which is therefore excreted in the urine, is derived from liver glycogen. A part of the glycogen deposited in the liver during glucose absorption is mobilized by epinephrine. This sugar cannot be utilized by the muscles, for an unknown reason, while the glucose which reaches the muscle directly from the intestine is utilized in a normal way.
Experiments with the same dose of epinephrine have also been made on rats in the post-absorptive state. As much glucose was fed by stomach tube as is absorbed in 4 hours, and the metabolism was determined during the 4 hours.
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