Correlation of kynurenine excretion with liver tryptophan pyrrolase levels in disease and after hydrocortisone induction.

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Abstract
Abnormal tryptophan metabolism occurs in many apparently unrelated diseases (rheumatoid arthritis, Hodgkin''s disease, schizophrenia, etc.). An assay system suitable for measuring the activity of tryptophan pyrrolase in needle biopsy samples of human liver was developed. In a group of hospitalized subjects, the tryptophan pyrrolase activity varied between 0.26 and 1.32 units and in the same patients, the excretion of kynurenine during 24 hr. after a 2-g oral dose of tryptophan ranged between 30 and 328 [mu]moles. The administration of hydrocortisone caused 2-4-fold increases in the level of tryptophan pyrrolase and in the amount of urinary kynurenine. In all the nutritionally normal subjects studied, including those given hydrocortisone, there was a direct correlation between the activity of tryptophan pyrrolase and the amount of urinary kynurenine. The results suggest that in a variety of diverse diseases (excluding pyridoxine deficiency) the high rate of excretion of kynurenine and its metabolites might be de to an increased rate of oxidation of tryptophan. The cause of this, the high level of liver tryptophan pyrrolase, may frequently be a result of increased adrenocortical secretion.
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