SYNTHESIS AND METABOLISM OF l‐KYNURENINE IN RAT BRAIN

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Abstract
Abstract— A method for the quantitative analysis of femtomole amounts of kynurenine (along with tryptophan, 3‐hydroxykynurenine and kynuramine) in rat brain using high pressure liquid chroma‐tography and electron‐capture GLC is described. Endogenous concentrations of these substances in rat brain regions were measured, and their formation after the injection of radioactive tryptophan or kynurenine was determined. Kynurenine was formed from tryptophan in brain and was also taken up from the periphery. Extracerebral kynurenine was calculated to account for 60% of the cerebral pool of kynurenine. The cerebral rates of synthesis of kynurenine and 3‐hydroxykynurenine were 0.29 and 0.17nmol/g/h. The turnover rate of kynurenine in the brain was 1.02 nmol/g/h measured from [14C]tryptophan or 1.14 nmol/g/h from [3H]kynurenine injected intraperitoneally. Kynuramine levels in different areas of the brain were similar to those of tryptamine. Following intraperitoneal injection of [14C]tryptophan, the presence of anthranilic, 3‐hydroxyanthranilic, xanthurenic, kynurenic and quinaldic acids was demonstrated in the brain.