Ascorbic acid synthesis from D-glucose-2-C14 in the liver of the intact rat.

Evidence that glucose1 is the ultimate g-carbon precursor of ascorbic acid in the rat was first obtained by Jackel, Mosbach, Burns, and King (1). They administered uniformly labeled glucose-C** to Chloretone-treated rats and recovered uniformly labeled ascorbic acid from the urine. Subsequently, Horowitz, Doerschuk, and King (2) and Burns and Mosbach (3) discovered that when glucose-l-C14 was administered to Chloretone-treated or normal rats, the urinary ascorbic acid was labeled primarily in C-6. Experiments employing glucose-6-Cl4 in Chloretonetreated rats resulted in urinary ascorbic acid labeled primarily in C-l (4). These tracer studies and the nonisotopic experiments of Isherwood, Chen, and Mapson (5) led to postulation of the following scheme of ascorbic acid biosynthesis in the rat: