Glyceride–glycerol release and the interconversion of glucose and glycerol in normal and fasted rats

Specific activities of plasma glycerol, plasma glucose, and respiratory CO2 were determined during continuous intra-arterial infusion of trace amounts of glycerol uniformly labelled with 14C into normal and 24-h fasted white rats. The same measurements were made in other rats during primed continuous infusion of glucose uniformly labelled with 14C. The data were analyzed by means of a previously described two-pool model in material and isotopic steady state. The two major precursors of plasma glycerol were considered to be glycerol from triglyceride hydrolysis and glycerol derived from glycolytic intermediates formed during the metabolism of glucose or glucogenic amino acids. The model allowed quantitative assessment of each source. In normal adult rats the rate of total net formation of plasma glycerol was 0.27 mg carbon per min per rat of which about 30% was ascribed to glyceride–glycerol release and 70% to net formation of glycerol from glycolytic intermediates. In fasted rats, the rate of total net fo...