Effect of pyridoxine on tryptophan metabolism in rheumatoid arthritis.

In a previous paper (Bett, 1962), it was reported that a majority of patients with rheumatoid arthritis excreted abnormal amounts of the tryptophan metabolites, 3-hydroxyanthranilic acid and kynurenine. In these experiments the most striking difference between control subjects and patients with rheumatoid arthritis was in the urinary kynurenine output after a loading dose of L-tryptophan. This work has been extended in the present investigation and the possible relationship between this abnormality and the duration or activity of disease has been explored. Kynureninase, one of the enzymes responsible for kynurenine catabolism, is dependent on pyridoxal phosphate (Jakoby and Bonner, 1953). For this reason, the effect of administration of pyridoxine on kynurenine output after tryptophan loading has been studied.