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Adenosinetriphosphatase activity of myosin in the conduction system of bovine heart
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25 ADENOSINETRIPHOSPHATASE ACTIGTY OF MYOSIN IN THE CONDUCTION SYSTEM OF BOVINE HEART. K.Saito, Y.Tamura, M.Saito, Second Department of K.Matsumura, T.Niki and H.Mori. Internal Medicine, School of Medicine, Tokushima University, Tokushima, Japan. The characteristics of the myosin ATPase in the conduction system (specialized heart muscle) of the bovine heart were studied biochemically in comparison with the ordinary heart muscle. The specialized heart muscle was composed of atrioventricular node, bundle of His, and right and left bundle branches. The yield of myosin protein from the specialized heart muscle was approximately 20% of that from the ordinary heart muscle. The EDTA- and Ca2+-activated ATPase activities of the myosin from the specialized heart muscle were both approximately 14% of those from the ordinary heart muscle. The specific activities of the myosin EDTA- and Ca2+-activated ATPase were not significantly different in the two types of heart muscle. When SDS-polyacrylamide gel electrophoresis was perthat myosin of the specializformed, it was demonstrated ed heart muscle contained three classes of light chains, whereas myosin of the ordinary heart muscle had only two.
26 ADRIAMYCIN INDUCED CARDIOMYOPATHY OF RATS - DECREASE IN MYOSIN B ATP-ASE ACTIVITY. K. Takahashi, N. Takeda, H. Maeno, M. Shiozaki, K. Kaito, T. Okubo, M. Nagano. Department of Internal Medicine, Jikei University, Tokyo, Japan. Adriamycin (ADR)was given to Wistar male rats intraperitoneally 0.5mg/kg per day for 5 days each week for 6 weeks. Myosin B ATPase activity of ADR cardiomyopathic hearts measured chronologically decreased gradually from 14th to 40th day after the initiation of the injection. And concomitant gradual increase of heavy chain component and decrease of actin component were shown by SDS gel electrophoresis in proportion to cumulative dose of ADR. We also studied superprecipitation of normal and ADR cardiomyopathic hearts, and the latter showed delayed completion of superprecipitation. ADR seems to inhibit contractile protein synthesis byinhibition of DNA synthesis. We also consider that depressed myosin B ATPase activity may be due to heart failure by ADRcardiomyopathy in addition to the direct effect of ADR on synthesis of contractile protein.
25 ADENOSINETRIPHOSPHATASE ACTIGTY OF MYOSIN IN THE CONDUCTION SYSTEM OF BOVINE HEART. K.Saito, Y.Tamura, M.Saito, Second Department of K.Matsumura, T.Niki and H.Mori. Internal Medicine, School of Medicine, Tokushima University, Tokushima, Japan. The characteristics of the myosin ATPase in the conduction system (specialized heart muscle) of the bovine heart were studied biochemically in comparison with the ordinary heart muscle. The specialized heart muscle was composed of atrioventricular node, bundle of His, and right and left bundle branches. The yield of myosin protein from the specialized heart muscle was approximately 20% of that from the ordinary heart muscle. The EDTA- and Ca2+-activated ATPase activities of the myosin from the specialized heart muscle were both approximately 14% of those from the ordinary heart muscle. The specific activities of the myosin EDTA- and Ca2+-activated ATPase were not significantly different in the two types of heart muscle. When SDS-polyacrylamide gel electrophoresis was perthat myosin of the specializformed, it was demonstrated ed heart muscle contained three classes of light chains, whereas myosin of the ordinary heart muscle had only two.
26 ADRIAMYCIN INDUCED CARDIOMYOPATHY OF RATS - DECREASE IN MYOSIN B ATP-ASE ACTIVITY. K. Takahashi, N. Takeda, H. Maeno, M. Shiozaki, K. Kaito, T. Okubo, M. Nagano. Department of Internal Medicine, Jikei University, Tokyo, Japan. Adriamycin (ADR)was given to Wistar male rats intraperitoneally 0.5mg/kg per day for 5 days each week for 6 weeks. Myosin B ATPase activity of ADR cardiomyopathic hearts measured chronologically decreased gradually from 14th to 40th day after the initiation of the injection. And concomitant gradual increase of heavy chain component and decrease of actin component were shown by SDS gel electrophoresis in proportion to cumulative dose of ADR. We also studied superprecipitation of normal and ADR cardiomyopathic hearts, and the latter showed delayed completion of superprecipitation. ADR seems to inhibit contractile protein synthesis byinhibition of DNA synthesis. We also consider that depressed myosin B ATPase activity may be due to heart failure by ADRcardiomyopathy in addition to the direct effect of ADR on synthesis of contractile protein.