Substrate use in ischemic and reperfused canine myocardium: quantitative considerations

Area of Science:

• Cardiology
• Metabolic Research
• Myocardial Reperfusion Injury

Background:

• Substrate utilization patterns in reperfused myocardium are not well understood.
• Accurate interpretation of Positiron Emission Tomography (PET) scans requires knowledge of myocardial substrate metabolism.
• Differentiating normal from abnormal heart muscle depends on understanding metabolic shifts.

Purpose of the Study:

• To investigate glucose and fatty acid utilization in normal, ischemic, and reperfused myocardium.
• To assess the contribution of glucose and fatty acid metabolism to overall oxidative metabolism in these conditions.
• To clarify substrate utilization patterns for improved interpretation of cardiac PET imaging.

Main Methods:

• Open-chest anesthetized dog model.
• Measurement of glucose and fatty acid utilization in normal, ischemic, and reperfused myocardium.
• Intracoronary administration of labeled substrates ([3H]glucose and [14C]palmitate).
• Sequential analysis of regional coronary venous blood samples.

Main Results:

• Reperfused myocardium showed significantly increased glucose utilization compared to ischemic and normal myocardium (273% increase vs. normal).
• Fatty acid utilization in reperfused myocardium was significantly lower than in normal myocardium (48% of control), despite restored blood flow.
• In reperfused myocardium, glucose contributed only 25% to oxidative metabolism, while fatty acid oxidation accounted for 63% of total oxygen consumption.

Conclusions:

• Canine myocardium reperfused after ischemia exhibits enhanced glucose uptake.
• There is impaired utilization of fatty acids in reperfused myocardium.
• These findings are crucial for interpreting metabolic changes in heart muscle post-reperfusion and optimizing cardiac imaging techniques.