The Glycogenolytic Effect of Adrenaline on the Isolated Rat Diaphragm.

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Abstract
Summary.: 1. The glycogenolytic effect of adrenaline on the isolated rat diaphragm is characterized by:a) The breakdown of glycogen is partial and does not exceed 25 per cent of the initial glycogen content.b) The glycogenolysis occurs rapidly and is at a maximum after 5 mins.c) The degree of glycogen breakdown is approximately the same in glucose‐free or glucose‐containing medium (140 mg per cent) while the increase in glucose concentration in the medium (500 mg per cent) partly counteracts the effect of adrenaline.d) The effect also occurs with mannose or fructose as substrate during incubation.e) The effect is at a maximum without requiring the addition of inorganic phosphate to the medium.2. The increase of the potassium concentration in the incubation medium inhibits the uptake of glucose and the glycogen synthesis in the diaphragm. The breakdown of glycogen in the diaphragm after the addition of adrenaline is not more pronounced with a high potassium concentration in the medium.3. n‐Butanol affects the inhibition of the normal glycogen synthesis, and the glycogenolytic effect of adrenaline becomes also more pronounced. After freezing and thawing of the diaphragm the ability of glycogen synthesis is abolished.4. On addition of adrenaline in vitro, a new metabolic equilibrium in the diaphragm takes place, characterized by a lower glycogen content and an increased content of hexose monophosphate. The mechanism of the adrenaline effect is discussed.