Relationship between alternate routes of tryptophan metabolism following administration of tryptophan peroxidase inducers or stressors

Abstract— Administration of glucocorticoids to rats increased the activity of hepatic tryptophan peroxidase (EC 1.11.1.4) and lowered brain serotonin. Pretreatment with glucose diminished both of these effects. Administration of allylisopropylacetamide to adrenalecto-mized rats increased both the activity of tryptophan peroxidase and the level of brain serotonin but had no effect on tryptophan hydroxylase (EC 1.99.1.4) activity in the brain stem. The activity of tryptophan peroxidase was increased by the acute stress of laparotomy and by the chronic stress of a 72-h fast. Neither stressor affected brain serotonin levels appreciably. These results argue against the proposal that the activity of tryptophan peroxidase activity directly affects synthesis of brain serotonin by diverting tryptophan from the biosynthesis of this monoamine.