Muscle twitching in isotonic sucrose solution.

Abstract

The possible cause of the twitching observable in the isolated sartorius muscle which had been immersed in isotonic sucrose solution was investigated. Macroscopic observation of the twitching, flame-photometric analysis for Na and K, and measurement of the membrane potential were performed with reference to the efflux experiments of isotopic Na and Ca.1. Presoaking solutions which resulted in the spontaneous contraction in the second immersion in isotonic sucrose were Ca free Ringer, acetate Ringer or 200mM Na Ringer, while those which did not initiate the contraction were normal Ringer, K free Ringer, glutamate Ringer or ouabain Ringer. The former group changed to the latter group in accordance with the change in chemical composition of the solution or with an addition of certain drug, and vice versa.2. Membrane depolarization or the absolute values of internal K and Na had no immediate relation to the sucrose twitch. The mobilization of internal Ca is supposed to be a principal factor of the twitch, and the internal Ca concentration available for the twitch has the optimum Ca concentration which makes the actomyosin labile and causes the irregular spontaneous repetition of the contraction. The possible cause for the sucrose twitch is the combination of the presence of the optimum Ca concentration and the breakdown of mutual normal ratio among internal Na, K, and Ca.3. The sucrose twitch is one special type of the muscle contraction which is produced under the condition without any extracellular electrolytes. The spontaneous, but transient, repetitive shortening of the actomyosin is able to be brought about by making the contractile elements labile with the breakdown of mutual normal equilibration among intracellular Na K, and Ca concentrations.