Über die Biosynthese von Lipiden aus Fructose in Leber, I. Einbau von uniform markierter [14C]Fructose in Leberlipide

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Abstract
Lipid biosynthesis in vivo in rat liver was studied in short term (10 min.) experiments following the intraportal infusion of [C14]fructose. The experiments were standardized by analysis of the stationary concentration of metabolites with fructose loading. The highest total C14.activity in the liver (30% of the administered [C14] fructose activity) is reached after 2.5 min. Subsequent loss of radio-activity is counteracted by the continued uptake of [C14]-fructose from the blood. From changes of C14-activity in blood and liver could be suggested that radioactivity of blood is mainly due to the administered [C14]fructose and not to its degradation products. The incorporation of C14-activity into the liver lipids is maximal after 2.5 min. (4.5% of the total radioactivity of the liver). The lipids were fractionated by column chromatography and analyzed for total radioactivity and specific radioactivity. The glycerol and fatty acid moieties were differentiated and the results are discussed. The rapid turn over of D-2,3-diglycerides is discussed in the light of accepted theories of lipid biosynthesis. The synthesis of cholesterol and fatty acids from the common [C14] acetyl-CoA pool proceeds at high velocity but low yield.