In vivo formation of pyridoxal phosphate schiff's base—an inherent defect in the tryptophan load test

Abstract

The excretion of xanthurenic acid by four adults following oral administration of up to 7 g (100 mg/kg) tryptophan, increases markedly with the size of the dose. The excretion of xanthurenic acid by adults is much larger than by children given a comparable dose on the basis of body weight. Administration of pyridoxine during the test reduced the excretion by an adult to the level seen in children. A possible interpretation of this is discussed. The results indicate the limits within which the tryptophan load test can be reproduced.