筋収縮に對するAdenosine體の作用

第2編 グリセリン處理筋と弛緩因子

抄録

The author has succeded in isolating a substance from skeletal muscle, which causes the relaxation of glycerol treated muscle in the presence of ATP. This substance, tentatively named “relaxing factor” by the author, is thermolabil and protein-like in nature, being effective at pH 6.0-7.0, and appears mostly in the fraction precipitated by 20 gm/dl of ammoninm sulfate. Glycerol treated muscle relaxed by the addition of “relaxing factor” can be again shortened by ATP, i.e. the contraction-relaxation cycle is able to be reversibly repeated. When a small amount of Ca is added to this muscle preparation thus relaxed, there happens a very rapid contraction which has never been observed in usual ATP contraction of glycerol treated muscle. This may probably be due to the inactivation of “relaxing factor” by Ca. This is consistent to the fact that Ca precipitant such as oxalate, fluoride or phosphate accelerates the relaxing action of this factor. The author believes that the discovery of “relaxing factor” may contribute to the clarification of the physiological mechanism in muscular contraction.