A quantitative gas chromatography-mass spectrometry (GC/MS) method was developed to measure nanomolar quantities of long-chain saturated beta-hydroxy fatty acids (12, 14, 16, and 18 carbons long) produced by isolated ischemic heart. Only beta-hydroxymyristate (25-40 nmol/g dry) was found in fresh heart. Isolated rabbit heart perfused with fatty acid by the nonrecirculating Langendorff technique produced negligible beta-hydroxy fatty acids. Ischemic perfusion with 0.25-0.75 mM palmitate prompted heart beta-hydroxy fatty acid accumulation, beta-hydroxypalmitate greater than beta-hydroxystearate, up to 100 nmol x g dry-1 x 10 min-1. beta-Hydroxy fatty acid production was proportional to coronary effluent lactate-to pyruvate ratio, did not continue beyond 10 min of ischemia, was dependent on exogenous fatty acid, and was inhibited by coperfusion with 10 mM acetate. Reperfusion for 5-10 min dissipated accumulated beta-hydroxypalmitate. Hypoxic perfusion prompted beta-hydroxy fatty acid production comparable to that with severe ischemia. These data show that during oxygen deficiency heart fatty acid beta-oxidation is not only depressed but is also incomplete; beta-hydroxy fatty acyl intermediates accumulate and contribute to the increased intracellular fatty acid content characteristic of the ischemic myocardium.

A B S T R A C T ,B-Hydroxymyristate, -palmitate, and -stearate were produced by and accumulated in isolated rabbit heart when perfused ischemically for 2-10 min by the nonrecirculating Langendorff technique with 0.75 mM palmitate and 0.16 mM albumin. Tissue fractionation into mitochondria and cytosol showed that by 2 min of ischemia 44% of ,B-hydroxypalmitate and 38% f,-hydroxystearate was located in the cytosol; this percentage increased to >50% by 5 min of ischemia. Lipid fractionation studies showed that by 10 min these two f.-hydroxy fatty acids were distributed approximately as 60% acylcarnitine, 20% acyl-coenzyme A (CoA), and 20% free fatty acids. All three chemical forms of ,B-hydroxypalmitate were found in both the mitochondria and the cytosol. After 10 min of ischemia f3-hydroxypalmitoyl-CoA and f3-hydroxystearoyl-CoA constituted at least 16% of the incremental long-chain acyl-CoA, whereas f#-hydroxypalmitoylcarnitine and ,B-hydroxystearoylcarnitine constituted -8% of the incremental long-chain acylcarnitine. These data suggests that myocardial f3-hydroxyacyl-CoA oxidation is limited during ischemia. Substrate accumulates and is transferred to the cytosol where it accumulates primarily as ,-hydroxyacylcarnitine.

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