Presence of kynurenic acid and kynurenine aminotransferases in the inner retina.
Kynurenine aminotransferases (KATs I and II) are pivotal to the synthesis of kynurenic acid (KYNA), the only known endogenous glutamate receptor antagonist and neuroprotectant. This study is the first to identify KYNA in the rat retina and to examine immunohistochemically the distribution of KAT isoforms. As determined by HPLC, KYNA concentration in the retina was 99.9 +/- 24.6 pmol/g wet wt. Immunohisto- chemical experiments showed that both KATs were present in the retina. KAT I was preferentially localised on Müller cell endfeet while KAT II was expressed in cells within the ganglion cell layer. In conclusion, KYNA is present and synthesised in the inner retina. This may suggest a modulatory role in glutamate-mediated retinal neurotransmission.
Rejdak
R
R
Department of Pathophysiology of Vision and Neuro-Ophthalmology, University Eye Hospital, Division of Experimental Ophthalmology, Röntgenweg 11, D-72076, Tübingen, Germany.
Zarnowski
T
T
Turski
W A
WA
Okuno
E
E
Kocki
T
T
Zagórski
Z
Z
Kohler
K
K
Guenther
E
E
Zrenner
E
E
D000818:Animals; D018698:Glutamic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D007736:Kynurenic Acid / Q000378:metabolism*; D009457:Neuroglia / Q000166:cytology / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000201:enzymology*; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017470:Receptors, Glutamate / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000201:enzymology*; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000378:metabolism; D009435:Synaptic Transmission / Q000502:physiology*; D000637:Transaminases / Q000378:metabolism*
D020033:Protein Isoforms; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D000637:Transaminases; C021481:kynurenine-oxoglutarate transaminase; D007736:Kynurenic Acid