Evaluation of Fatty Acid Metabolism in Hearts After Ischemia-Reperfusion Injury Using a Dual-Isotope Autoradiographic Approach and Tissue Assay for Metabolites of Tracer

We investigated whether changes in myocardial uptake of fatty acid tracer after reperfusion following transient myocardial ischemia were closely related to alterations in intracellular fatty acid oxidation. Using a fatty acid tracer of (131)I- and (125)I-labeled 15-(p-iodophenyl)-9-methylpentadecanoic acid (9MPA), the myocardial uptake and metabolites were determined by dual-tracer autoradiography and thin-layer chromatography in rats 3 or 14 d after reperfusion following 5 or 15 min of ischemia induced by coronary artery ligation. 9MPA metabolites processed via beta-oxidation were lower in the ischemic region (IR) than in non-IR 3 d after 5 min of ischemia, despite no reduction of tracer uptake in IR. Oxidation of 9MPA was recovered 14 d after 15 min of ischemia in association with normalization of tracer uptake in IR, whereas both uptake and oxidation of 9MPA were markedly impaired 3 d after 15 min of ischemia, accompanied by slow clearance of myocardial tracer. Normal uptake of fatty acid tracer early after reperfusion does not always imply preserved intracellular fatty acid oxidation. However, reduction of tracer uptake might reflect impaired fatty acid oxidation.