Title: The alteration of Ca^|^ldquo;-dependent ATPase and ^|^rdquo;Ca-calcium uptake in sarcoplasmic reticulum of atrophied muscles derived from vitamin E deficient rats
Abstract: Using highly purified fraction of sarcoplasmic eticulum of skeletal muscles, Km value of Ca2+-dependent ATPase and the velocity of 45Ca-calcium uptake into the vesicles were measured in the atrophied muscles derived from the deficient rats. For comparison, similar measurements were made also in control muscles. Chemical properties of the enzyme were analyzed in the same specimen.The production of the vitamin deficiency and therewith induced muscle atrophy were judged by the following criteria : 0 Vitamin E concentration in serum and liver was markedly decreased in the fifth week of the feeding on vitamin deficient diet ; R The level of creatine phosphokinase activity in serum became several times higher than that of the control in the fourth week ; R Electron-microscopic examination of the heart and skeletal muscles revealed the signs of muscle atrophy were observed clearly in the 22 nd week. Km value became smaller and the velocity of 45Ca-calcium uptake became higher as the muscle atrophy advanced. The maximum values of them were observed in the 22 nd week after the onset of the experiment. Molecular weights and electrophoretic mobilities of Ca2+-dependent ATPase in both conditions were similar. These findings suggest the presence of the compensatory mechanism, which automatically facilitates the contractile ability of atrophied muscles by increasing the velocity of Ca2+ uptake into the vesicles.