Fatty Acid Oxidation by Skeletal Muscle During Rest and Activity

¹ From the Department of Physiology, University of Michigan, Ann Arbor, Michigan

The metabolism of C¹⁴-labeled acetate, octanoate and palmitate by isolated skeletal muscle (latissimus dorsi and diaphragm) from normal, fed rats has been examined. The rates at which these substrates were converted to C¹⁴O₂ have been shown to vary with concentration, temperature, functional state of the muscle, and the presence of albumin. Increased concentration of fatty acids led to enhanced conversion of substrate to C¹⁴O₂. Electrical stimulation of muscles under tension resulted in approximately a 60% increase in oxygen consumption and about a 100% rise in fatty acid oxidation. The addition of glucose did not alter the rate of fatty acid metabolism by muscle. The addition of bovine albumin at concentrations up to approximately 1 µm albumin/7 µm palmitate resulted in augmented palmitic acid oxidation. However, at concentrations of albumin greater than 1 µm albumin/7 µm palmitate, palmitic acid degradation by resting diaphragm was inhibited, suggesting a firmer binding of fatty acid to albumin. The Q₁₀ for palmitic acid oxidation by resting diaphragm was 2.23 in the absence of added albumin between 25° and 37°C. The data are discussed in relation to the present concepts of fat metabolism and transport in vivo. It is suggested that fat degradation in isolated muscle may provide an energy source during activity.

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