Induction of Tryptophan Pyrrolase in Rat Liver by Physiological Amounts of Hydrocortisone and Secreted Glucocorticoids

Abstract

Assays of the fully activated tryptophan pyrrolase in rat liver show that the enzyme level is increased in five hours to a tenfold maximum by 0.25 mg of administered hydrocortisone or by the stimulation of adrenal gland secretion. Both inductions cause higher levels in male than female rats. The tryptophan pyrrolase level can serve as an index of the physiological secretion of glucocorticoids.

Liver and Brain Tryptophan Metabolism Following Hydrocortisone Administration to Rats and Gerbils

“…Furthermore, addition of an equal volume of gerbil homogenate to a rat liver homogenate had no effect on either conjugation or activity of the rat pyrrolase as measured by the method of Knox et al (1966).…”

“…While addition of tryptophan and the co-factor haematin activates the enzyme in whole homogenates this only occurs after a time lag (Knox & Ogata, 1965). We therefore also attempted to measure pyrrolase activity in cell supernatants following either preincubation with methaemoglobin (Knox et al, 1966) or thermal activation (Schutz & Feigelson, 1972), both techniques being designed to ensure that all enzyme present is converted to the active reduced holoenzyme before assay. Even with these assay systems no significant enzyme activity was found in the gerbil.…”

“…Adult male gerbils 50-90 g ( (Knox, Piras & Tokuyama, 1966), or thermal activation, when the soluble liver fraction was incubated at 55C for 5 min, chilled, centrifuged and the supernatant used (Schutz & Feigelson, 1972). Measurement of pyrrolase activity in liver homogenates was essentially by the method of Knox & Auerbach (1955) in which whole liver homogenates are incubated in the presence of 0.003 M tryptophan, except that 2 x 10-6M haematin was added to the reaction mixture (Kevitz & Wagner, 1965).…”

l-Tryptophan: Effects on daytime sleep latency and the waking EEG

“…Many metabolic factors may act to alter the availability of 1-tryptophan to the brain at different times in the diurnal cycle (Knox, 1966;Knox, Piras, & Tokuyama, 1966;Azmitia & McEwen, 1969;Hardeland, 1969;Fernstrom & Wurtman, 1972;Tagliamonte, Biggio, Vargiu, & Gessa, 1973;Curzon & Knott, 1974;Gessa & Tagliamonte, 1974), and it has been previously suggested that 1-tryptophan may have hypnotic effects only in nighttime administration (Cooper, 1979). We conducted this study of 1-tryptophan to determine its effects on the waking and sleep EEG and to assess its hypnotic efficacy in daytime administration.…”

Biochemistry of Depression

“…Curzon and Green (20) decided to use rats to test whether the high pyrrolase levels are maximal only a few hours after injection of hydrocortisone (30).…”