Further observations on the biosynthesis of L-ascorbic acid from D-glucose in the rat.

Previous studies showed that the intact carbon chain of glucose can serve as a precursor for the synthesis of ascorbic acid in the rat (l-3). Evidence for such a precursor relationship came from experiments in which glucose tracers labeled in carbon 1 and carbon 6 were administered to rats, and the L-ascorbic acid isolated from urine was labeled predominantly in carbon 6 and carbon 1, respectively. This type of labeling in the ascorbic acid molecule would be expected if the glucose carbon chain is converted without fragmentation to ascorbic acid. These studies were carried out in rats in which the synthesis of ascorbic acid was markedly accelerated by the administration of the hypnotic drug Chloretone. No information was available, however, on the precursors of ascorbic acid in the normal rat. For this reason, in the present study the incorporation of glucose-l-C?* into urinary ascorbic acid was compared in normal and Chloretone-treated rats. The results presented in this paper indicate that glucose is a precursor of ascorbic acid in normal rats as well as in Chloret’one-treated rats.