Peak power output in skinned cardiac myocytes and isolated working hearts decreased as a nearly linear function of increasing beta-MyHC expression (r2 = 0.82 to 0.85).
Does the level of beta-MyHC expression affect power output in rat cardiac myocytes and isolated working hearts?
Power output in both single cardiac myocytes and whole working hearts is highly dependent on and linearly inversely related to beta-MyHC expression.
Effect estimate: r2 = 0.85
The amount of work the heart can perform during ejection is governed by the inherent contractile properties of individual myocytes. One way to alter contractile properties is to alter contractile proteins such as myosin heavy chain (MyHC), which is known to demonstrate isoform plasticity in response to disease states. The purpose of this study was to examine myocyte functionality over the complete range of MyHC expression in heart, from 100% alpha-MyHC to 100% beta-MyHC, using euthyroid and hypothyroid rats. Peak power output in skinned cardiac myocytes decreased as a nearly linear function of beta-MyHC expression during maximal (r2 = 0.85, n = 44 myocyte preparations) and submaximal (r2 = 0.82, n = 31 myocyte preparations) Ca2+ activation. To determine whether single myocyte function translated to the level of the whole heart, power output was measured in working heart preparations expressing varied ratios of MyHC. Left ventricular power output of isolated working heart preparations also decreased as a linear function of increasing beta-MyHC expression (r2 = 0.82, n = 34 myocyte preparations). These results demonstrate that power output is highly dependent on MyHC expression in single myocytes, and this translates to the performance of working left ventricles.
Korte et al. (2005) studied Myosin heavy chain (MyHC) expression in euthyroid and hypothyroid rats. beta-MyHC expression vs. alpha-MyHC expression was evaluated on Peak power output in skinned cardiac myocytes and left ventricular power output in isolated working hearts (r2 = 0.85). Peak power output in skinned cardiac myocytes and isolated working hearts decreased as a nearly linear function of increasing beta-MyHC expression (r2 = 0.82 to 0.85).