EFFECT OF COMPOUNDS RELATED TO GLYCOLYSIS IN MUSCLE ON THE SENSITIVITY OF MUSCLE TO ACETYLCHOLINE AND POTASSIUM

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Abstract
The effect of products of glycolysis, substances involved in the esterification of carbohydrates, and substances inhibiting glycolysis (a) on the rectus abdominis muscle of the frog, and (b) on the acetylcholine and (c) potassium sensitivity of this muscle, was investigated. Hexosediphosphate, adeno-sinetriphosphate, fluoride, citrate, and oxalate in relatively high concentrations induced shortening of the muscle in the absence of any other agent. The acetylcholine sensitivity: (a) increased by hexosediphosphate, pyruvic acid, acetone, acetaldehyde, adenosinetriphosphate, creatinephosphate, creatinine, inosinic acid, epinephrine, physostigmine, and fluoride (some by inhibition of the cholinesterase, some by other mechanisms); (b) not modified by dihydroxyacetone monophosphate, [beta]-glycerophosphate, propionic acid, acetic acid, acetoacetate, ethylalcohol, creatine, ammonia, pyrophos-phate, glyceraldehyde, monoiodoacetate, citrate, oxalate, and phosphate; (c) decreased by butyric acid (high concentrations) and [beta]-hydroxybutyric acid. The potassium sensitivity: (a) decreased by epinephrine, in biological concentrations, acetaldehyde and /3-hydroxybutyric acid in higher concentrations, and immersion in potassium-free Ringer''s solution and Ringer''s solution with high calcium content; (b) not modified by propionic acid, acetone, ethyl alcohol, creatinephosphate, glyceraldehyde, and monoiodoacetate; (c) increased by the other substances used. There seems to be no direct relationship between activity of -SH groups and changes in acetylcholine and potassium sensitivity of the muscle. It is inferred from the above experiments that: (1) measures lowering the calcium ion content of the muscle increase the potassium sensitivity and induce shortening of the muscle; (2) changes in distribution or in increase of intracellular adenosinetriphosphate increase the acetylcholine sensitivity of the muscle. The data are compatible with the postulate that changes in amount or distribution of intracellular adenosinetriphosphate is an. important factor in the initiation of muscle contraction.