Elevated levels of a calcium-activated muscle protease in rapidly atrophying muscles from vitamin E-deficient rabbits |
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Authors: | William R Dayton Judith V Schollmeyer Alvin C Chan CEugene Allen |
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Institution: | 1. Department of Animal Science, University of Minnesota, St. Paul, MN 55108, U.S.A.;2. Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55427 U.S.A. |
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Abstract: | A Ca2+-activated proteolytic enzyme 1 that partially degrades myofibrials was isolated from hind limb muscles of normal rabbits and rabbits undergoing rapid muscle atrophy as a result of vitamin E deficiency. Extractable Ca2+-activated protease activity was 3.6 times higher in muscle tissue from vitamin E-deficient rabbits than from muscle tissue of control rabbits. Ultrastructural studies of muscle from vitamin E-deficient rabbits showed that the Z disk was the first myofibrillar structure to show degradative changes in atrophying muscle. Myofibris prepared from muscles vitamin E-deficient rabbits showed partial or complete loss of Z-disk density. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the amount of troponin-T (37 000 daltons) and α-actinin (96 000 daltons) was reduced in myofibrils from atrophying muscle as compared to myofibrils prepared from control muscle. In vitro treatment of purified myofibrils with purified Ca2+-activated proteolytic enzyme produced alterations in myofibrillar ultrastructure that were identical to the initial alterations occuring in myofibrils from atrophying muscle (i.e. weakening and subsequent removal of Z disks). Additionally the electrophoretic banding pattern of Ca2+-activated proteolytic enzyme-treated myofibrils is very similar to that of myofibrils prepared from muscles atrophying as a result of nutritional vitamin E deficiency. The possible role of Ca2+-activated proteolytic enzyme in disassembly and degradation of the myofibril is discussed. |
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Keywords: | Vitamin E Myofibril Protease (Rabbit muscle) |
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