Quantitative Studies on Human Urinary Metabolites of Tryptophan as Affected by Isoniazid and Deoxypyridoxine1

The Effect of Vitamin Supplementation on the Urinary Excretion of Tryptophan Metabolites by Pregnant Women*

“…In livers from pyridoxine-deficient animals, a decrease in kynureninase activity was observed (9,10). In humans with a functional pyridoxine deficiency induced by isoniazid or deoxypyridoxine (Figure 1) kynurenine were excreted, but excretior mal when the diet was supplemented doxine (27). In contrast, the low ex o-aminohippuric acid by the pregnan in this study was not increased by pyrido plements ( Table I), suggesting that per monal factors were in some way inhi kynureninase activity.…”

“…In Figure 1 is shown graphically the average post-tryptophan excretion levels of nonpregnant and pregnant women receiving no vitamin supplements, and for comparison, the excretion patterns of a male subject who received deoxypyridoxine and isoniazid at different periods (27). The excretion pattern of the pregnant group is noticeably different from that of the controls and differs from the patterns observed with deoxypyridoxine and isoniazid chiefly in that pregnant subjects excreted larger amounts of pyridone than did subjects with either of the drug-induced abnormalities.…”

Effect of Oral Contraceptives on Tryptophan and Tyrosine Availability: Evidence for a Possible Contribution to Mental Depression

“…This may be due to competition between the estro gen conjugates and pyridoxal phosphate for the concerned enzymes since similar excre tion patterns have been demonstrated follow ing pyridoxine depletion (51,52). The nor mal and elevated plasma levels of kynurenine and tryptophan, respectively, as presently found, together with the lack of effect of com bined OC to increase the basal urinary kynur enine excretion (42, 43), do not indicate a definite elfect of estrogen on the initial and rate-limiting step (53, 54) of tryptophan ca tabolism.…”

The Antipyridoxine Effect of Penicillamine in Man*

“…The increased urinary excretion of the intermediary metabolites of tryptophane (xanthurenic acid and kynurenine) that occurs in patients treated with isoniazid has led to the concept that that drug is a metabolic antagonist of vitamin B, (13). The co-administration of this vitamin with isoniazid has favorably influenced certain of the toxic manifestations of the drug without impairing its efficacy (14).…”