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Analysis of azide-insensitive Ca2+-dependent ATPase activity in atrial specimens from patients with coronary or
Insights
Heart failure significantly reduces myofibrillar ATPase activity in atrial tissue. This enzymatic inhibition, linked to altered ATP kinetics and reduced protein thiol content, impacts cardiac function in patients with heart disease.
Area of Science:
- Biochemistry
- Cardiology
- Molecular Biology
Background:
- Myofibrillar ATPase activity is crucial for cardiac muscle contraction.
- Heart failure is associated with significant alterations in myocardial energy metabolism.
- Understanding enzymatic changes in atrial tissue during heart failure is vital for therapeutic development.
Purpose of the Study:
- To investigate the activity of azide-insensitive Ca2+-dependent ATPase in atrial specimens from patients with heart disease.
- To compare enzymatic activity between patients with and without left ventricular heart failure.
- To explore the relationship between enzyme kinetics, ATP binding, and protein thiol content in failing hearts.
Main Methods:
- Enzymatic assays were performed on atrial tissue samples from patients undergoing cardiac surgery.
- Azide-insensitive Ca2+-dependent ATPase activity was measured.
- Kinetic parameters (Km and Vmax) for ATP were determined.
- Protein thiol group content was quantified in tissue homogenates.
Main Results:
- Significantly lower myofibrillar ATPase activity was observed in atrial specimens from patients with left ventricular heart failure compared to controls.
- Enzyme inhibition was characterized by an increased Km and a reduced Vmax for ATP, particularly in left atrial fragments.
- Failing heart atrial homogenates showed a reduced content of protein thiol groups.
Conclusions:
- Left ventricular heart failure leads to a marked reduction in atrial myofibrillar ATPase activity.
- The observed decrease in enzymatic activity is associated with altered ATP binding kinetics and diminished protein thiol content.
- These biochemical changes in atrial tissue may contribute to the pathophysiology of heart failure.
Abstract:
The activity of the azide-insensitive Ca2+-dependent ATPase (highly enriched in myofibrillar ATPase activity) was studied in specimens of both right and left atria which were taken from patients with ischemic and/or valvular heart disease during coronary by pass and/or valvular substitution. A significantly lower enzymatic activity was found in atrial specimens from patients with left ventricular heart failure in comparison to the atrial fragments obtained from the patients with normal heart function. Such an inhibition reflected a significant increase in the Km of the enzyme for ATP and was associated with a concomitant reduction in Vmax, both more evident in the left atrial fragments. Moreover, tissue homogenates of atrial specimens from failing hearts exhibited a lower protein SH group content when compared to the atrial homogenates from the heart with normal left ventricular heart function.