Tissue Distribution and Uptake of Endogenous Lipoprotein Triglycerides in the Rat*

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Abstract
The tissue distribution of endogenously produced lipoprotein triglyceride was studied in rats maintained on ordinary laboratory pellet diets. At least 95% of endogenous circulating triglycerides synthesized from circulating free fatty acids (FFA) are found in lipoproteins of density < 1.019 with the predominant fraction having a density less than 1.006. Triglyceride activity equilibrated rapidly with liver. Triglycerides reentered adipose tissue and were taken by skeletal muscle. Incorporation into phospholipid fatty acid was active in muscle and liver but less so in adipose tissue. Transformation of palmitate to other fatty acids in the formation of triglyceride fatty acid was minimal. The liver performed no essential role in relation to uptake of triglyceride by adipose tissue or muscle. Endogenous formation of lipoprotein triglyceride may be a mechanism for redeposition in adipose tissue of excess circulating free fatty acids.