Control of bovine hepatic fatty acid oxidation

Abstract Fatty acid oxidation by bovine liver slices and mitochondria was examined to determine potential regulatory sites of fatty acid oxidation. Conversion of 1-[ 14 C]palmitate to 14 CO 2 and total [ 14 C] acid-soluble metabolites was used to measure fatty acid oxidation. Oxidation of palmitate (1m M ) was linear in both liver slice weight and incubation time. Carnitine stimulated palmitate oxidation; 2m M dl-carnitine produced maximal stimulation of palmitate oxidation to both CO 2 and acid-soluble metabolites. Propionate (10m M ) inhibited palmitate oxidation by bovine liver slices. Clofenapate, an inhibitor of fatty acid esterification, alone increased palmitate oxidation and was able to prevent the propionate-induced inhibition of palmitate oxidation by liver slices. Propionate (.5 to 10m M ) had no effect on palmitate oxidation by mitochondria, but malonyl Coenzyme A, the first committed intermediate of fatty acid synthesis, inhibited mitochondrial palmitate oxidation (inhibition constant=.3 µ M ). Liver mitochondrial carnitine palmitoyltransferase (EC 2.3.1.21) exhibited Michaelis constants for palmitoyl Coenzyme A and 1-carnitine of 11.5 µ M and .59m M , respectively. Long-chain fatty acid oxidation in bovine liver is regulated by mechanisms similar to those in rats but adapted to the unique digestive physiology of the bovine.