Relationship between the ATPase activity, actomyosin and cardiac myofibrils of dogs, rats and frogs and their physiological characteristics
Kiselev, V.D.
Kardiologiia 19(1): 107-112
1979
ISSN/ISBN: 0022-9040 PMID: 35640 Document Number: 153392
Results of experiments on actomyosin in the heart of adult dogs, white rats and the frog R. esculenta confirmed that the ATP cleavage rate does not depend on physiological fluctuations in ATP concentration. The maximum ATPase activity was observed in the actomyosin of the rat ventricle and dog auricle and the minimal in the dog and frog ventricles. The same experiments on myofibrils revealed similar relationships as in actomyosin but there was a significant dependence of cleavage rate on variations in ATP concentration. A similar dependence is characteristic of human skeletal and cardiac muscles. Myofibril ATPase is inhibited by ADP and by a decrease in pH. The combination of the high activity of the myofibril ATPase and its dependence on ATP concentration with the considerable lowering of ATP and concentration of ADP explains the drop in contractility of the rat heart during high frequency rhythm workouts.