Increased cyclic AMP content accelerates protein synthesis in rat heart

Area of Science:

• Cardiovascular Physiology
• Molecular Biology
• Biochemistry

Background:

• Cyclic AMP (cAMP) is a crucial second messenger involved in various cellular processes, including cardiac function.
• Protein synthesis regulation in the heart is vital for maintaining cardiac health and function.
• Understanding the signaling pathways that control protein synthesis is essential for developing therapeutic strategies for cardiac diseases.

Purpose of the Study:

• To investigate the role of cyclic AMP (cAMP) in regulating protein synthesis in the rat heart.
• To determine whether mechanical stimuli, such as elevated aortic pressure, influence cardiac protein synthesis through cAMP-dependent pathways.
• To elucidate the signaling mechanisms by which insulin and other agents affect cardiac protein synthesis.

Main Methods:

• Isolated perfused rat heart models were used to study protein synthesis rates under various conditions.
• Agents that elevate cAMP (glucagon, forskolin, IBMX) were administered to assess their impact on protein synthesis.
• Contractile activity was manipulated using tetrodotoxin and by altering aortic pressure.
• Insulin's effects on protein synthesis and cAMP levels were examined.
• Muscarinic-cholinergic agonism was used to probe signaling pathways.

Main Results:

• Elevating cAMP levels with glucagon, forskolin, or IBMX increased protein synthesis rates, even when contractile activity was arrested.
• Increased aortic pressure accelerated protein synthesis and elevated cAMP content and cAMP-dependent protein kinase activity.
• Insulin enhanced protein synthesis but did not increase cAMP levels; however, elevated pressure in insulin-treated hearts increased cAMP.
• Methacholine blocked pressure-induced increases in cAMP and protein synthesis, suggesting a muscarinic-cholinergic involvement in the pressure response.
• Pertussis toxin treatment disrupted the inhibitory effect of methacholine, indicating a role for Gi/o proteins.

Conclusions:

• Elevation of cardiac cyclic AMP (cAMP) promotes protein synthesis through mechanisms independent of contractile activity.
• Increased aortic pressure stimulates cardiac protein synthesis via a cAMP-dependent pathway that involves muscarinic-cholinergic signaling.
• Insulin accelerates cardiac protein synthesis through a cAMP-independent mechanism.