In this study, we tested the hypotheses that 1) diabetes-induced disturbances in cardiac my-ATPase activity would be attributed to not only myosin heavy chain (MHC) isoform transitions, but also reduced amounts in MHC...In this study, we tested the hypotheses that 1) diabetes-induced disturbances in cardiac my-ATPase activity would be attributed to not only myosin heavy chain (MHC) isoform transitions, but also reduced amounts in MHC protein;and 2) if diabetes results in declines in the MHC protein content, this change would relate to oxidative damage to MHC. Diabetes was induced by a single intraperitoneal injection of streptozotocin. After 6 weeks of injection, the left ventricles were excised for mechanical and biochemical analyses. Peak twitch tension and the rate of force development in papillary muscles were decreased by 23.4% and 34.1%, respectively. A 33.5% reduction in myofibrillar ATPase activity occurred in conjunction with a 9.5% decrease in MHC protein as well as MHC isoform transitions towards a slower phenotype. The decreased MHC content was not accompanied by elevations in carbonyl groups present in MHC. Whole muscle analyses indicated that the contents of malondialdehyde and reduced glutathione were elevated. These results suggest that decreases in the MHC content may be associated, at least in part, with a diabetes-related inactivation of cardiac my-ATPase and may not be due to accumulation of oxidative damage to protein.展开更多
文摘In this study, we tested the hypotheses that 1) diabetes-induced disturbances in cardiac my-ATPase activity would be attributed to not only myosin heavy chain (MHC) isoform transitions, but also reduced amounts in MHC protein;and 2) if diabetes results in declines in the MHC protein content, this change would relate to oxidative damage to MHC. Diabetes was induced by a single intraperitoneal injection of streptozotocin. After 6 weeks of injection, the left ventricles were excised for mechanical and biochemical analyses. Peak twitch tension and the rate of force development in papillary muscles were decreased by 23.4% and 34.1%, respectively. A 33.5% reduction in myofibrillar ATPase activity occurred in conjunction with a 9.5% decrease in MHC protein as well as MHC isoform transitions towards a slower phenotype. The decreased MHC content was not accompanied by elevations in carbonyl groups present in MHC. Whole muscle analyses indicated that the contents of malondialdehyde and reduced glutathione were elevated. These results suggest that decreases in the MHC content may be associated, at least in part, with a diabetes-related inactivation of cardiac my-ATPase and may not be due to accumulation of oxidative damage to protein.
