The total carbohydrate content of isolated frog muscle

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Abstract
A modification of the method of estimating total carbohydrate of muscle by hydrolysing the whole muscle is described. A modification of Bissinger''s method of separating sugar from solution and estimating it quantitatively by precipitation with Cu-lime, using the Cu as the oxidizing agent for sugar estimation is described. The resting value of the total carbohydrate of isolated frog muscles estimated by this method was much greater than the sum of the glycogen and alcohol-soluble carbohydrate. During incubation in a phosphate buffer at pH 8 this excess carbohydrate is removed from the muscle but does not appear as lactic acid. The lactic acid increase is in general somewhat greater than the decrease of the sum of glycogen and alcohol-soluble carbohydrate. The excess carbohydrate is not removed during incubation in 2% bicarbonate buffer. In muscles poisoned with monoiodoacetic acid, during anaerobiosis and fatigue the total carbohydrate content does not change significantly whilst the glycogen content falls. The lactic acid content rises very slightly on the average. The alcohol-soluble carbohydrate rises but not sufficiently to account for the fall in glycogen. When the total carbohydrate of muscle is estimated by this method there is left in the muscle a small residual amount of glycogen, on the average 50 mgm. per 100 gm. muscle. This glycogen does not change significantly in amount during incubation in phosphate buffer. Approximately the same amount of glycogen remains after incubation when the whole glycogen content of the muscle is es- timated by Pfluger''s method. It is suggested that this glycogen may be of a different nature from the main bulk of that present in muscle.