Studies on Actomyosin of Heart Muscle

抄録

Superprecipitation, ATPase activity of actomyosin, and isometric tension of glycerol-extracted muscle fibers, and also the action of ouabain on these actomyosin preparations were investigated on the skeletal and cardiac, both normal and experimentally failing, muscles of dogs. There were no qualitative differences between skeletal and cardiac muscle actomyosin. Superpercipitation and ATPase activity were depressed in actomyosin prepared from right ventricles compared with that from left ventricles of the dogs with surgically induced right-sided heart failure. Isometric tension-development, on the other hand, was reduced in both ventricles. Low concentrations of ouabain improved superprecipitation, both did not affect ATPase activity. Tension-development was unaffected in a Ca free medium, but in a Ca containing medium, the inhibitory action of 10^-2∼10^-3 M of Ca was eliminated by this concentrations of ouabain. High concentrations, on the other hand, depressed superprecipitation, ATPase activity, and also tension-development. In contrast to low concentrations, high concentrations of ouabain enhanced the inhibitory action of Ca on tension-development. These actions of ouabain in various concentrations were similary observed in all of skeletal, and both normal and failing cardiac muscles.