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Lysosomal and neutral hydrolase activity during the regression of cardiac hypertrophy
Insights
Cardiac hypertrophy in rats involves changes in enzymes like acid RNase and beta-glucuronidase. A calcium-activated neutral protease (CAF) was identified that degrades alpha-actinin in cardiac muscle.
Area of Science:
- Cardiovascular Biology
- Enzymology
- Molecular Muscle Physiology
Background:
- Cardiac hypertrophy, induced by aortic constriction in rats, leads to significant changes in cardiac tissue.
- Understanding the molecular mechanisms of cardiac remodeling and regression is crucial for cardiovascular health.
Purpose of the Study:
- To investigate the enzymatic changes during the development and regression of cardiac hypertrophy.
- To characterize a specific protease involved in cardiac muscle protein degradation.
Main Methods:
- Induction of cardiac hypertrophy via aortic constriction in a rat model.
- Measurement of enzyme activities (RNase, beta-glucuronidase, cathepsin D, neutral protease) at various time points.
- Isolation, partial purification, and characterization of Ca2+-activated neutral protease (CAF).
- Assessment of CAF's effect on myofibrillar proteins, specifically alpha-actinin.
Main Results:
- Aortic constriction elevated acid RNase and beta-glucuronidase activities, indicating tissue breakdown.
- Left ventricular weight and RNA content rapidly decreased upon removal of the constricting band.
- Cathepsin D and alkaline RNase activities remained unchanged during hypertrophy and regression.
- Ca2+-activated neutral protease (CAF) was isolated and shown to degrade alpha-actinin in myofibrils.
Conclusions:
- Specific proteases, including acid RNase and beta-glucuronidase, are involved in cardiac hypertrophy regression.
- Ca2+-activated neutral protease (CAF) plays a role in degrading key muscle proteins like alpha-actinin during cardiac remodeling.
Abstract:
Cardiac hypertrophy was produced in rats by constriction of the ascending aorta. Removal of the constricting band 10 days after operation resulted in rapid decline in left ventricular (LV) weight and total ventricular RNA. Activities of acid RNase and beta-glucuronidase were elevated 3 days after aortic constriction. Activities of cathepsin D and alkaline RNase were unchanges. Activities of cathepsin D and acid RNase were unchanged 1 and 3 days after removal of constricting band. Ca2+-activated, neutral protease (CAF) isolated from postmitochondrial muscle supernatant was partially purified and characterized. CAF specifically degrades alpha-actinin when incubated with isolated myofibriles in the presence of Ca2+.