ABSTRACT
This chapter describes most of the methods that have been published for the determination of tryptophan metabolites in urine will be reviewed and selected procedures. The assessment of vitamin B6 nutritional status will also be considered, with particular reference to urinary 4-pyridoxic acid and plasma pyridoxal phosphate determinations, and the use of erythrocyte alanine aminotransferase assays. The chapter discusses interpretation of the data obtained by these methods in pregnant and oral contraceptive treated women and an appraisal made of their clinical significance. Although studies of tryptophan metabolism have provided pointers toward this possibility, assessment of vitamin B6 nutrition in women receiving these preparations also requires the application of methods which are not affected by enzyme induction or other hormonal effects. Interference with tryptophan metabolite analyses by drugs is of particular concern when colorimetric procedures are used in conjunction with ion-exchange chromatography.
