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Z.F. Zagorski, R.A. Rejdak, E. Zielinska, Y. Shenk, T. Zarnowski, W. Turski, E. Zrenner, K. Kohler; Enzymatic Activity of Kynurenine Aminotransferase I (KAT I) and its Cellular Expression in the Chicken Retina During Ontogeny . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1654.
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Purpose: Kynurenine aminotransferases (KAT I and II) are pivotal for the synthesis of kynurenic acid (KYNA) and both KYNA and KATs are present in the retina. After showing developmental changes of KYNA content in rat and chicken retinas (Rejdak et al. 2002) the present study examine KAT I activity and its cellular expression in avascular chicken retina during ontogeny. Material and methods: Retinas from White Leghorn chickens at different developmental stages between embryonic day (E12) and post-hatching day 7 (P7) were used. KAT I enzymatic activity was investigated with HPLC. Immunohistochemistry was performed using specific antibodies against KAT I and glutamine synthetase as a marker for Müller cells. Results: Cellular expression of KAT I was present in chicken retina in all examined developmental stages. Double labelling studies showed its presence on Müller cell endfeet what was in agreement with results from the rat retina (Rejdak et al. 2001). HPLC measurements revealed marked differences in KAT I activity between the embryonic and post-hatching stages. In 12-day-old embryonic (E12) retinas the KAT I activity was of 1.2 ± 0.36 pmol/ mg protein and 3.05 ± 0.9 pmol/mg protein in E16 embryos. It significantly decreased to 1.4 ± 0.4 at P0 and stayed at a similar level (1.1 ± 0.3 pmol/mg protein) at P7. Conclusion: KAT I is present in the chicken retina. Both its enzymatic activity and cellular expression are higher in early developmental stages. This may suggest a modulatory role in glutamate-mediated neurotransmission in the chicken retina during development.
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