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Cardiac contractile protein synthesis: Does the pattern change in stress?
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CARDIAC CONTRACTILE PROTEIN SYNTHESIS: DOES THE PATTERN CHANGE IN STRESS? Schreiber, S.S., Evans, C-D., Oratz, M., Rothschild, M.A. Dept. Nuclear Med., VA Hospital & Dept. Medicine, New York University School of Medicine, NY. The functioning sarcomere appears microscopically unchanged with stresses, such as pressure overload, but does this mean that there are parallel changes in synthesis of contractile proteins? We have studied such synthesis in vitro in the guinea pig in response to pressure stress, with aging, and after prolonged ethanol ingestion and have found the synthetic alterations which occur are not uniform. Even under control conditions, contractile proteins have different relative synthetic rates (TM>HC>A>LCl>LC2) and molar synthesis does not necessarily follow the molar proportions indicating that turnover rates are not the same. With increased afterload in the young, there is initial increase in relative synthesis of HC (compared to LC's). With aging, the relative synthesis of HC falls, and with application of afterload stress, there This difference between is no increase in relative HC synthesis. young and adult may be related to the difference in myosin ATPase. On the other hand, with pressure stress in the adult there is an increase in relative synthesis of actin. In contrast, when the young animal is exposed to ethanol ingestion during growth, there is a fall in total protein synthesis with no fall in synthetic rate of contractile proteins except for that of actin. Thus, despite the necessity to maintain the integrity of the sarcomere structure following stresses, subtle changes in contractile protein synthesis may occur and may also reflect in later functional changes.
CARDIAC CONTRACTILE PROTEIN SYNTHESIS: DOES THE PATTERN CHANGE IN STRESS? Schreiber, S.S., Evans, C-D., Oratz, M., Rothschild, M.A. Dept. Nuclear Med., VA Hospital & Dept. Medicine, New York University School of Medicine, NY. The functioning sarcomere appears microscopically unchanged with stresses, such as pressure overload, but does this mean that there are parallel changes in synthesis of contractile proteins? We have studied such synthesis in vitro in the guinea pig in response to pressure stress, with aging, and after prolonged ethanol ingestion and have found the synthetic alterations which occur are not uniform. Even under control conditions, contractile proteins have different relative synthetic rates (TM>HC>A>LCl>LC2) and molar synthesis does not necessarily follow the molar proportions indicating that turnover rates are not the same. With increased afterload in the young, there is initial increase in relative synthesis of HC (compared to LC's). With aging, the relative synthesis of HC falls, and with application of afterload stress, there This difference between is no increase in relative HC synthesis. young and adult may be related to the difference in myosin ATPase. On the other hand, with pressure stress in the adult there is an increase in relative synthesis of actin. In contrast, when the young animal is exposed to ethanol ingestion during growth, there is a fall in total protein synthesis with no fall in synthetic rate of contractile proteins except for that of actin. Thus, despite the necessity to maintain the integrity of the sarcomere structure following stresses, subtle changes in contractile protein synthesis may occur and may also reflect in later functional changes.