Nitric oxide controls cardiac substrate utilization in the conscious dog

Area of Science:

• Cardiovascular Physiology
• Metabolic Regulation
• Nitric Oxide Signaling

Background:

• Nitric oxide (NO) plays a crucial role in cardiovascular function.
• Cardiac substrate utilization is vital for maintaining heart energy demands.
• The specific impact of NO synthase inhibition on cardiac metabolism requires further elucidation.

Purpose of the Study:

• To investigate the effects of acute nitric oxide (NO) synthase inhibition on cardiac substrate utilization.
• To determine if a NO donor can reverse these metabolic changes.
• To understand the regulatory role of NO in cardiac metabolism.

Main Methods:

• Administered nitro-L-arginine (NLA) intravenously to instrumented dogs to block NO synthase.
• Collected hemodynamic and blood samples from aorta and coronary sinus.
• Utilized a NO donor and angiotensin II infusion in separate groups to assess reversibility and hemodynamic mimicry.

Main Results:

• NLA administration led to increased myocardial oxygen consumption (MVO2) and a shift towards carbohydrate oxidation (lactate and glucose uptake increased, fatty acid uptake decreased).
• The observed metabolic changes were reversed by the administration of a NO donor.
• Angiotensin II infusion mimicked some hemodynamic effects but did not replicate the full metabolic shift.

Conclusions:

• Acute inhibition of NO synthase significantly alters cardiac substrate utilization, favoring carbohydrates.
• NO plays a critical regulatory role in controlling cardiac metabolic pathways.
• NO donors can effectively reverse the metabolic consequences of NO synthase inhibition in the heart.