Chronic nonocclusive coronary artery constriction in rats. Beta-adrenoceptor signal transduction and ventricular...

Area of Science:

• Cardiovascular Physiology
• Molecular Cardiology
• Cardiac Metabolism

Background:

• Chronic coronary artery constriction can lead to cardiac dysfunction.
• Understanding the impact on beta-adrenoceptor signaling is crucial for cardiac health.

Purpose of the Study:

• To investigate the effects of chronic coronary artery constriction on cardiac function.
• To examine the regulation of beta-adrenoceptor signal transduction in response to sustained reduced coronary blood flow.

Main Methods:

• Surgical narrowing of the left main coronary artery in rats, creating a moderate stenosis.
• Assessment of cardiac function, including left ventricular end-diastolic pressure and dP/dt.
• Radioligand binding assays to quantify beta-adrenoceptor density and affinity.
• Measurement of agonist-stimulated adenylate cyclase activity and cyclic AMP generation.
• Analysis of ADP ribosylation of a 45-kD substrate.

Main Results:

• A 44% reduction in coronary luminal diameter caused increased left ventricular end-diastolic pressure and decreased cardiac contractility (dP/dt).
• Global cardiac hypertrophy was evident, with increased left and right ventricular weights.
• In the failing left ventricle, beta-adrenoceptor density, agonist-stimulated adenylate cyclase activity, and substrate ADP ribosylation were depressed.
• In the hypertrophic but non-failing right ventricle, beta-adrenoceptor density was preserved, but agonist-stimulated cyclic AMP generation and substrate quantity were reduced.

Conclusions:

• Long-term, moderate coronary artery stenosis has detrimental effects on cardiac contractile performance.
• Adrenergic support mechanisms are significantly attenuated in the setting of chronic coronary constriction.
• Cardiac hypertrophy and failure are associated with impaired beta-adrenergic signal transduction, affecting both failing and non-failing ventricles.