Free fatty acid metabolism by skeletal muscle

Abstract

Removal and oxidation of free fatty acids (FFA) were studied by the electrically stimulated skeletal muscle in dogs receiving an infusion of I-C¹⁴-palmitate, oleate, linoleate, or octanoate. Resting skeletal muscle removed about 43% of the arterial FFA. The A-V difference was directly proportional to the arterial FFA level. During electrical stimulation the removal increased due to the increased blood flow while the extraction ratio decreased. A portion of the infused carbon 14 appeared in the venous blood as C¹⁴O₂ in all animals receiving either long-chain fatty acids or octanoate. The specific activity of C¹⁴O₂ in the venous blood became higher than that in the arterial blood during stimulation when long-chain fatty acids were infused, but did not undergo such changes when octanoate was infused. No differences were observed between the different groups of animals receiving the various long-chain fatty acids. It is postulated that only a fraction of the removed FFA is immediately oxidized, while a portion is stored and oxidized at a later date.