Metabolism of free fatty acids by myocardium and kidney

Abstract

The myocardial and renal removal and oxidation of plasma free fatty acids (FFA) were studied in dogs receiving an infusion of I-C¹⁴-palmitate, oleate, linoleate, or octanoate. The myocardium extracted about 40% of the total arterial FFA, and some was oxidized to CO₂. Blood C¹⁴O₂ was consistently higher in the coronary sinus than in the artery. The specific activity of the coronary sinus C¹⁴O₂ was higher than that of the arterial C¹⁴O₂ in dogs infused with long-chain fatty acids. The specific activity of arterial C¹⁴O₂ was higher than that of the coronary sinus C¹⁴O₂ when octanoate was infused. There were no differences observed in FFA extraction and C¹⁴O₂ production among the different groups of animals receiving the various long-chain fatty acids. In gas chromatographic studies palmitic acid was the only FFA with a consistent net removal by the kidney. Approximately 9% of the arterial radiopalmitate was removed by this organ in dogs receiving infusions of palmitic acid-1-C¹⁴. Simultaneously, C¹⁴O₂ was produced by the kidney. A consistent removal of oleate-1-C¹⁴ or a significant production of C¹⁴O₂ was not found. Infusion of octanoate-1-C¹⁴ led to a marked release of C¹⁴O₂ by the kidney, with greatly increased CO₂ specific activity in the renal vein.