The Effect of Adrenalline on the Glycogen Metabolism of Smooth Muscle

Summary.The effect of adrenaline on the glycogen metabolism of smooth muscle was investigated in experiments on rabbit gut, bovine tracheal muscle and coronary arteries, and guinea‐pig uterus. The glycogenolytic effect was correlated with the lactic acid stimulating and the relaxing effects.On rabbit gut, adrenaline had only a glycogenolytic effect in the absence of glucose. The decrease of glycogen was substantially less than the equivalent increase in the lactic acid content, and occurred later than the lactic acid production.In experiments on tracheal muscle adrenaline had a glycogenolytic effect of the same order of magnitude as the lactic acid production. Adrenaline and c had a synergistic glycogenolytic action, but an antagonistic effect on the tonus.Glycolysis inhibiting substances such as Cu++, Ca++, NaF, NaN3, and Na2HAsO4, which inhibited the lactic acid producing and the relaxing effects of adrenaline, similarly depressed its glycogenolytic action on tracheal muscle. With partial inhibition of the relaxing effect, the same applied to the glycogenolytic one too.Calcium ions and sodium azide had a stimulating effect on the glycogenolysis, but other glycolysis inhibiting drugs reduced the spontaneous glycogenolysis.Glucose abolished the blocking action of sodium azide on adrenaline's relaxing effect.In coronary arteries adrenaline produced glycogenolysis equivalent to the lactic acid production.On guinea‐pig uterus adrenaline had only a glycogenolytic effect in the experiments where distinct inhibition of the tonus or pendulum movements was obtained; in those where the relaxing effect was absent, the glycogen content rose in relation to the controls.Cori and Sutherland (1951) showed that adrenaline stimulates glycogenolysis in liver tissue and striated muscle by activating the enzyme phosphorylase, which catalyzes the reaction glycogen + phosphoric acid ⇌ glucose‐1‐phosphate. The effect of adrenaline on the glycogenolysis and lactic acid production in smooth muscle cannot be attributed solely to activation of this reaction; rather, adrenaline probably has at least one further point of interference in the carbohydrate metabolism.