Stimulation of liver tryptophan pyrrolase during heat exposure

Abstract

Exposure of rats to heat (39 +/- 1 degree C) stimulated liver tryptophan pyrrolase 2-fold between 3 and 48 h. Plasma corticosterone increased 2-fold after 1 h of heat exposure and decreased to a low value of 50% by 16 h. The effect of heat exposure on the enzyme was obtained in adrenalectomized animals. Stimulation by cortisol and tryptophan of the enzyme was also obtained in heat exposure, and the effects seemed to be additive. The concentration of tryptophan in the liver remained unchanged, and that in the plasma decreased to about 50% at 8 h exposure to heat and reverted to normal by 46 h. Simultaneous administration of noradrenaline to heat-exposed rats had no effect, whereas that of thyroxine partly prevented the stimulation of the enzyme activity. Hypothyroid conditions obtained by thyroidectomy or treatment with propylthiouracil significantly stimulated the enzyme activity. Cycloheximide treatment of heat-exposed rats did not prevent the stimulation of the enzyme activity. The results indicate that the effect of heat exposure on liver tryptophan pyrrolase is obtained, due to the accompanying hypothyroid condition, by increasing the activity of the existing protein by a mechanism possibly different from those known at present.

Stress-Induced Increase in Kynurenic Acid as a Potential Biomarker for Patients With Schizophrenia and Distress Intolerance

“…15 Stress is also associated with the onset and progression of symptoms in adolescence 16 and is often linked to exacerbation of psychotic symptoms in adulthood. 17 In animal models, stressors robustly induce TDO activity 18,19 and thereby stimulate the formation of KYNA and other KP metabolites, 20,21 in part through activation of the hypo-thalamic-pituitary-adrenal axis. 22,23 Stress also increases kynurenines through IDO, an enzyme typically regulated by cytokines.…”

Redox Properties of Tryptophan Metabolism and the Concept of Tryptophan Use in Pregnancy

“…The relation between HS and Trp metabolism has been detected in animals [ 209 , 210 , 211 ]. In rats, HS stimulated the increase of Trp pyrrolase in liver during 3 and 48 h exposures [ 209 ].…”

“…The relation between HS and Trp metabolism has been detected in animals [ 209 , 210 , 211 ]. In rats, HS stimulated the increase of Trp pyrrolase in liver during 3 and 48 h exposures [ 209 ]. The concentration of Trp in liver was unchanged, but Trp in the plasma was reduced by half after 8 h exposure to HS and returned to normal by 46 h [ 209 ].…”

“…In rats, HS stimulated the increase of Trp pyrrolase in liver during 3 and 48 h exposures [ 209 ]. The concentration of Trp in liver was unchanged, but Trp in the plasma was reduced by half after 8 h exposure to HS and returned to normal by 46 h [ 209 ]. In broiler chickens, HS significantly increased plasma Trp concentrations at 30 min exposure [ 210 , 211 ].…”

Tryptophan: The key to boosting brain serotonin synthesis in depressive illness

“…Other augmenters include thyroid hormones and the β-adrenoceptor antagonist pindolol. Although TDO activity is not influenced by thyroidectomy, tri-iodothyronine (T 3 ) administration causes inhibition (Franzone et al, 1980) and thyroxine inhibits the increase in TDO activity induced by heat exposure (Manjunath and Ramasarma, 1985). The effects of the β-adrenoceptor blocker pindolol on TDO activity have not been studied.…”