Synthesis in Vitamin-Deficient Animals

There have been several papers published which suggest that the synthesis of ascorbic acid is impaired in vitamin-deficient animals, with the conclusion that the action of this or that vitamin is necessary at one stage in the synthetic process. It is appropriate to review briefly here the evidence on which such conclusions are based. 

Observations that a deficiency of vitamin A induces scurvy-like alterations in teeth (Johnson et al., 1942, 1945) are also suspect, since it is well established that a deficiency of the vitamin leads to marked degenerative changes in the dentine and enamel of teeth, which cannot be cured by ascorbic acid, but only by vitamin A (Wolbach and Howe, 1933 Boyle, 1933 Mellanby, 1939). 

The evidence would therefore suggest that the lowered ascorbic acid content of tissues of vitamin A-deficient animals is due to inanition associated with the deficiency rather than to any specific effect of vitamin A on the synthesis of ascorbic acid. 

The fact that the physiological condition produced by hypervitaminosis A, unlike that of scurvy, does not respond to ascorbic acid would indicate that no specific relationship between synthesis of ascorbic acid and vitamin A intake exists. 

The synthesis of ascorbic acid in animals has also been linked with thiamine and riboflavin (Kennaway and Daff, 1946 Roy et al., 1946). With both these deficiencies the ascorbic acid content of the tissue of rats and mice has been shown to be low. The stimulation of synthesis shown by a normal animal after chloretone treatment was not observed in animals deficient in either thiamine or riboflavin. The claim was made 

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