beta-Hydroxy fatty acid production by ischemic rabbit heart.

Abstract

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.

Amphipathic metabolites and membrane dysfunction in ischemic myocardium.

“…It occurs first in the mitochondrial fraction, followed by progressive increases in the cytosolic fraction during the first 10 minutes. Nearly 60% is in the form of /3-hydroxypalmitoyl carnitine in the cytosol, with only 15% as the CoA ester (Moore et al, 1982). Although this represents only 8% of the total acyl carnitine, the results suggest that rapid inhibition of /8-oxidation can lead to accumulation of not only precursors (i.e., acyl CoA), but also intermediates of /3-oxidation.…”

“…Although this represents only 8% of the total acyl carnitine, the results suggest that rapid inhibition of /8-oxidation can lead to accumulation of not only precursors (i.e., acyl CoA), but also intermediates of /3-oxidation. It appears that these intermediates can react with carnitine acyl transferase as well as carnitine translocase for exchange out of the mitochondria to the cytosol (Moore et al, 1982). This possibility is supported by observations indicating that /3-hydroxy palmitoyl carnitine is an avid substrate for carnitine acyl transferase (Al-Arif and Blecher, 1971).…”

“…This was initially suggested by findings obtained in isolated mitochondria wherein increases in the NADH:NAD ratio or inhibition by rotenone increased accumulation of /3-hydroxy palmitate (Bremer and Wojtczak, 1972;Hull et al, 1975). More recent studies by Hull and coworkers indicate that, in ischemic isolated perfused rabbit hearts, j8-hydroxy palmitate and stearate accumulate (Hull et al, 1976;Moore et al, 1980Moore et al, , 1982. Small increases in /3-hydroxy palmitate are found in effluents from ischemic isolated perfused hearts (Moore et al, 1980).…”

Inhibition of mitochondrial β-oxidation in the heart by increased redox state of the ubiquinone pool

“…Inhibition of the respiratory chain, as occurs in cardiac ischaemia, could therefore lead to inhibition of P-oxidation either by inhibition of 3-hydroxyacyl-CoA dehydrogenase or the acyl-CoA dehydrogenases. Studies carried out in the perfused heart observed accumulation of 3-hydroxyacyl-esters during ischaemia, suggesting inhibition of the 3-hydroxyacyl-CoA dehydrogenase [3,4]. However, other studies found that 3-hydroxyacyland 2-enoyl-CoA esters only formed a small percentage of the CoA esters accumulated [S] and that incubation of intact mitochondria with cyanide, mimicking cardiac ischaemia, did not lead to accumulation of 3-hydroxyacyl-esters but incubation with rotenone, a complex I inhibitor, did lead to their accumulation [6].…”

“…Studies carried out in the perfused heart observed accumulation of 3-hydroxyacyl-esters during ischaemia, suggesting inhibition of the 3-hydroxyacyl-CoA dehydrogenase [3,4]. However, other studies found that 3-hydroxyacyland 2-enoyl-CoA esters only formed a small percentage of the CoA esters accumulated [S] and that incubation of intact mitochondria with cyanide, mimicking cardiac ischaemia, did not lead to accumulation of 3-hydroxyacyl-esters but incubation with rotenone, a complex I inhibitor, did lead to their accumulation [6].In order to resolve the question of which step of P-oxidation is inhibited during cardiac ischaemia, we incubated cardiac mitochondria with 90pM [U-'4C]hexadecanoyl-CoA and measured P-oxidation flux and intact CoA esters [7] accumulated during inhibition of the respiratory chain with increasing amounts of myxothiazol, a complex 111 inhibitor. Parallel incubations were used to measure the redox states of the NAD'MADH pool and ubiquinondubiquinol pools [8,9].…”