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beta-Hydroxy fatty acid production during fatty acid oxidation by heart mitochondria.

The effect of various incubation conditions on the production of beta-hydroxylaurate, -myristate, and -palmitate by isolated rabbit heart mitochondria oxidizing palmityl carnitine was studied. A gas chromatographic-mass spectrometric method was developed to identify and measure submicrogram quantities of methyl esters of these beta-hydroxy fatty acids (FA). Alpha-Deuterated esters of beta-hydroxy-FA served as internal standards. The total amount of the three beta-hydroxy-FA in fresh mitochondria was 0.045 mug/mg of protein. Malate, ATP, rotenone, and 1-carnitine together effected an NADH:NAD ratio of 8 and the accumulation of 0.896 mug of beta-hydroxylpalmitate. Omission of carnitine decreased the beta-hydroxy-FA by 65 percent. Omission of palmityl carnitine resulted in no beta-hydroxy-FA. Without rotenone the NADH:NAD ratio was 0.5 and there accumulated only 0.085 mug of beta-hydroxy-FA/mg of protein/10 min. Succinate, in place of malate, effected an NADH:NAD ratio greater than 10 but only 0.465 mug of beta-hydroxy-FA/mg of protein/10 min. We conclude that elevated mitochondrial NADH:NAD ratios facilitate beta-hydroxy-FA accumulation by slowing beta-hydroxyacyl-CoA oxidation. Cardiac hypoxia may prompt beta-hydroxy-FA accumulation and/or release.