The Metabolism of Albumin Bound C14-Labeled Unesterified Fatty Acids in Normal Human Subjects

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Abstract
The metabolism of plasma unesterified fatty acids (UFA) was studied after intravenous injection of carboxyl-labeled palmitic, oleic, and linoleic acids and measurement of the rate of removal of labeled UFA carboxyl C from the plasma and its excretion in expired CO2. Flux of UFA from the plasma varied with nutritional state, ranging from 0.09 to 1.5 meq/minute. Approximately 10.% of labeled C from palmitic or oleic acids was recovered in CO2, in the 1st hour. From calculation of isotopic flux from the plasma it appeared that a large proportion of the labeled acids recycled 1 or more times in the plasma before oxidation, indicating plasma UFA flux to be greater than the utilization of UFA for energy. Recycling of linoleic acid appeared to be greater than for the oleic or palmitic acids. Labeled UFA appeared quickly in plasma neutral lipids. A general scheme for plasma UFA metabolism is discussed.