L. W. Mapson

The synthesis of ascorbic acid in the rat deprived of vitamin A with and without addition of chloretone.

There is as yet little evidence that any direct metabolic relationship exists in the organism between the water-soluble and fat-soluble vitamins. In the last 10 years, however, a growing interest has developed in the possibility of an interdependence between vitamins A and C. Work on this subject has been limited, and the results of previous experiments are confusing and inconclusive. The problem investigated has been mainly that of the effect of vitamin A deficiency oh the ascorbic acid content of the blood and other body tissues. Rats and cattle appear to have been the chief animals used in these investigations. Sure, Theis & Harrelson (1939) found that single or repeated depletion of vitamin A caused a fall in the concentration of ascorbic acid in the tissues of rats. The main organs affected were the kidney, heart, liver and thymus gland. In order to eliminate any possible effect of inanition resulting from the vitamin A deficiency, these workers made preliminary experiments from which they concluded that fasting up to a period of X I days produced no change in the ascorbic acid content of the rats tissues. Extending this work, they subsequently studied the effect of deficiencies of vitamins B, and B, and riboflavin, and found that an even greater loss of ascorbic acid from the tissues occurred in riboflavin deficiency. Sutton, Kaeser & Hansard (1942) fed young rats with graded doses of vitamin A for a period of 2 months and found that the level of ascorbic acid in the plasma ran parallel with the vitamin A intake. They state also that the urinary excretion of ascorbic acid in rats on a vitamin A-free diet was lower than that of control animals receiving adequate amounts of the vitamin. Apparently no attempt was made to control the food intake of any of the rats. This occurrence of diminished urinary excretion of ascorbic acid in vitamin A-deficient rats was confirmed by Boyer, Phillips, Pounden, Jensen, Rupel & Nesbit (1942), who found that the fall was more marked in female than in male animals. These workers suggest that absence of vitamin A decreases the concentration of ascorbic acid in the tissues by interfering with its synthesis and not by causing excessive loss from the kidneys. Once again there was no control of food intake. Jonsson, Obel & Sjoberg (1942, 1945) claim that a deficiency of vitamin A in rats produced scurvy-like alterations in the teeth, in addition to a fall in the blood content of ascorbic acid. These dental changes were not affected by giving vitamin C, but after the administration of vitamin A the condition improved and the blood values for ascorbic acid rose. The fact that deficiency of vitamin A leads to marked degenerative changes in the dentine and enamel of teeth has, however, been recognized for many years (Wolbach & Howe, 1933; Boyle, 1933; Mellanby & King,