A Study of Ascorbic Acid Synthesis by Animal Tissue in Vitro* by C. v. Smythe and C. G. King

It is well known that the tissues of albino rats, without an external source of vitamin C, contain appreciable concentrations of ascorbic acid as measured by staining techniques, chemical titration, and biological assay. The relative distribution and absolute concentrations appear to be fairly constant and regulated by synthesis in vivo, under most conditions of dietary regimen, but extreme variations in diet and in specific chemical treatment have been reported to induce measurable changes in the distribution and possibly in the total body content of ascorbic acid. Far more striking than the changes in tissue concentration, however, are the changes that can be induced in urinary excretion. When the animals are given a diet of natural foods and fed 20 to 50 mg. per day of such compounds as chloretone, chloral hydrate, or certain barbituric acid derivatives, the urinary excretion of the vitamin commonly rises from approximately 0.2 mg. per day to a range of 10 to 50 mg. per day (1, 2). Lesser degrees of increased excretion are caused by a large number of compounds (3,4). A point of special interest has been the correlation between substances that cause an increased excretion of glucuronic acid in some animals and ascorbic acid, or both acids, in others. The preliminary observation that 3-carbon intermediates of carbohydrate metabolism caused an increase in ascorbic acid synthesis (5), although glucose did not, led to a further possible analogy between