Content of Kynurenic Acid and Activity of Kynurenine Aminotransferases in Mammalian Eyes

The present study investigated the kynurenic acid (KYNA) contents and kynurenine aminotransferase (KAT I and II) activity in structures of the human, monkey, rabbit and bovine eye. KYNA levels were investigated with HPLC and detected fluorimetrically. The activity of KAT I and II was assayed as quantitative analysis of newly synthesized KYNA in vitro. Mean KYNA levels (±SD) in the human retina and vitreous body were 36.8 ± 7.6 and 33.1 ± 6.2 pmol/g wet tissue weight, respectively. In human eyes, KAT I activity in the vitreous body was 0.57 ± 0.28, that of KAT II was 2.56 ± 0.69. KAT I activity in the retina was 3.42 ± 1.17 and that of KAT II 10.75 ± 9.2. (KAT activity is expressed as KYNA synthesis in picomoles per gram wet tissue weight per hour.) The values of KYNA and KAT observed in other mammalian species tested were in the same range. In conclusion, KYNA and KAT enzymatic activity are present in the structures of human and other mammalian eyes.

[1]  E. Zrenner,et al.  Ontogenic changes of kynurenine aminotransferase I activity and its expression in the chicken retina , 2003, Vision Research.

[2]  E. Zrenner,et al.  Alterations of kynurenic acid content in the retina in response to retinal ganglion cell damage , 2003, Vision Research.

[3]  Z. Kleinrok,et al.  Endothelium-dependent production and liberation of kynurenic acid by rat aortic rings exposed to L-kynurenine. , 2002, European journal of pharmacology.

[4]  E. Zrenner,et al.  Changes of kynurenic acid content in the rat and chicken retina during ontogeny , 2002, Graefe's Archive for Clinical and Experimental Ophthalmology.

[5]  E. Zrenner,et al.  Presence of kynurenic acid and kynurenine aminotransferases in the inner retina , 2001, Neuroreport.

[6]  K. Blennow,et al.  Kynurenic acid levels are elevated in the cerebrospinal fluid of patients with schizophrenia , 2001, Neuroscience Letters.

[7]  T. Stone.  Kynurenines in the CNS: from endogenous obscurity to therapeutic importance , 2001, Progress in Neurobiology.

[8]  W. Turski,et al.  Evidence for Intraocular Synthesis of Kynurenic Acid, a Putative Endogenous Neuroprotectant , 2001, Ophthalmic Research.

[9]  W. Turski,et al.  Kynurenine aminotransferase I activity in human placenta. , 2001, Placenta.

[10]  H. Scharfman,et al.  Electrophysiological effects of exogenous and endogenous kynurenic acid in the rat brain: studies in vivo and in vitro , 2000, Amino Acids.

[11]  C. Post,et al.  Brain concentrations of kynurenic acid after a systemic neuroprotective dose in the gerbil model of global ischemia , 1999, Progress in Neuro-Psychopharmacology and Biological Psychiatry.

[12]  R. Schwarcz,et al.  Characterization of rat brain kynurenine aminotransferases I and II , 1997, Journal of neuroscience research.

[13]  M. Kreutz,et al.  Systemic L-kynurenine administration partially protects against NMDA, but not kainate-induced degeneration of retinal ganglion cells, and reduces visual discrimination deficits in adults rats. , 1996, Investigative ophthalmology & visual science.

[14]  S. Lipton,et al.  Greater sensitivity of larger retinal ganglion cells to NMDA-mediated cell death. , 1994, Neuroreport.

[15]  M. Beal,et al.  Neuroprotective Effects of L-Kynurenine on Hypoxia—Ischemia and NMDA Lesions in Neonatal Rats , 1992, Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism.

[16]  R. Schwarcz,et al.  Two kynurenine aminotransferases in human brain , 1991, Brain Research.

[17]  R. Schwarcz,et al.  Rat Brain Slices Produce and Liberate Kynurenic Acid upon Exposure to l‐Kynurenine , 1989, Journal of neurochemistry.

[18]  P. Andiné,et al.  The excitatory amino acid antagonist kynurenic acid administered after hypoxic-ischemia in neonatal rats offers neuroprotection , 1988, Neuroscience Letters.

[19]  G. Lombardi,et al.  Presence of Kynurenic Acid in the Mammalian Brain , 1988, Journal of neurochemistry.

[20]  R. Schwarcz,et al.  Identification and quantification of kynurenic acid in human brain tissue , 1988, Brain Research.

[21]  K. Shibata,et al.  Fluorimetric micro-determination of kynurenic acid, an endogenous blocker of neurotoxicity, by high-performance liquid chromatography. , 1988, Journal of chromatography.

[22]  R. Schwarcz,et al.  Kynurenic acid blocks neurotoxicity and seizures induced in rats by the related brain metabolite quinolinic acid , 1984, Neuroscience Letters.

[23]  T. Stone,et al.  An iontophoretic investigation of the actions of convulsant kynurenines and their interaction with the endogenous excitant quinolinic acid , 1982, Brain Research.