Relationship between the myofibrillar ATPase activity of human biopsy material and hemodynamic parameters.

Changes in gene expression in the intact human heart. Downregulation of alpha-myosin heavy chain in hypertrophied, failing ventricular myocardium.

“…Using gel electrophoresis, Alousi et al (61) reported two distinct MHC bands, with a fast-migrating band presumably corresponding to ␣-MHC; however, these authors could not detect a difference between normal and failing hearts (61). A similar finding was reported by Takeda et al (63), who reported in LV biopsy specimens a fast-migrating MHC band on gel electrophoresis that was 25-35% of the total, which paradoxically correlated with a decrease in myofibrillar ATPase activity in the same specimens. Kawana et al (64) reported ␣-MHC fluorescence labeling in only a "few" myofibrils from normal human ventricular myocardium procured from autopsy specimens, but a striking increase in ␣-MHC positivity in ventricles from heart failure patients treated with the ␤-agonist dobutamine (64).…”

Changes in myofibrillar content and Mg-ATPase activity in ventricular tissues from patients with heart failure caused by coronary artery disease, cardiomyopathy, or mitral valve insufficiency.

“…It is possible that a similar process involving the accumulation of skeletal muscle a-actin messenger RNA also occurs in failed human ventricle, and the replacement of cardiac actin by skeletal muscle actin could be a factor responsible for the reduction in myofibrillar MgATPase. Takeda et al 26 reported that there are no enzymatic differences in the Ca 2+ -activated Mg-ATPase activity of myofibrils of nonhypertrophied and hypertrophied papillary muscles removed from patients during mitral valve surgery. The absolute values for myofibrillar Mg-ATPase activity obtained in our study and those reported by Takeda et al 26 are somewhat comparable since the isolation of myofibrillar proteins and the composition and temperature of the reaction mixture used in the assay of Mg-ATPase activity were very similar in the two studies.…”

“…Takeda et al 26 reported that there are no enzymatic differences in the Ca 2+ -activated Mg-ATPase activity of myofibrils of nonhypertrophied and hypertrophied papillary muscles removed from patients during mitral valve surgery. The absolute values for myofibrillar Mg-ATPase activity obtained in our study and those reported by Takeda et al 26 are somewhat comparable since the isolation of myofibrillar proteins and the composition and temperature of the reaction mixture used in the assay of Mg-ATPase activity were very similar in the two studies. The values we reported for myofibrillar Mg-ATPase activity for ventricular myofibrils of normal human hearts are considerably higher than values obtained for hearts of patients in end-stage failure and values obtained for hearts of patients with mitral valve insufficiency or aortic stenosis reported by Takeda et al 26 These results imply that the myofibrillar Mg-ATPase activity is as depressed in ventricles of patients who are candidates for valve replacement surgery (pre-end-stage failure) as has been found for hearts of transplant candidates (end-stage failure).…”