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Modulation of myosin in right ventricular hypertrophy
Recent Advances in Studies on Cardiac Structure and Metabolism
|January 1, 1975
Summary
Pressure overload in dogs with early right ventricular hypertrophy increases myosin ATPase activity. This is linked to altered myosin subunit proportions, suggesting reduced light chain inhibition contributes to augmented myosin function.
Area of Science:
- Cardiovascular Physiology
- Cardiac Hypertrophy Research
- Molecular Cardiology
Background:
- Systolic pressure overload is a key factor in cardiac hypertrophy.
- Understanding molecular adaptations in the hypertrophied ventricle is crucial for therapeutic development.
Purpose of the Study:
- To investigate the impact of pressure overload on myosin activity and subunit composition in early canine right ventricular hypertrophy.
- To elucidate the role of myosin light chains in regulating myosin ATPase activity during cardiac stress.
Main Methods:
- Induction of mild pulmonic stenosis in dogs to create pressure overload.
- Comparison of hypertrophied right ventricles (HRV) with normal right ventricles (NRV) three weeks post-constriction.
- Assessment of myosin ATPase activity (Vmax) and myosin subunit proportions (heavy and light chains) using biochemical assays and two-dimensional gel electrophoresis.
Main Results:
- HRV showed a significant increase in heart/body weight compared to NRV.
- Myosin ATPase activity (Vmax) was significantly elevated in HRV for both K+ and Ca++ activation.
- The proportion of myosin light chains to heavy chains decreased in HRV, suggesting altered myosin structure.
Conclusions:
- Pressure overload elevates K+- and Ca++-activated myosin in early canine HRV.
- Reduced myosin light chain inhibition of myosin ATPase activity is a likely mechanism for augmented myosin function.
- Myosin light chain addition to HRV myosin lowered its ATPase activity, supporting a regulatory role.