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Elevated concentrations of kynurenic acid, a tryptophan derivative, in dense nuclear cataracts.

AbstractPURPOSE:
Kynurenines and their glycoside derivatives in the ocular lens absorb ultraviolet radiation and thus possibly help protect the retina from ultraviolet light. The current study analysed kynurenine aminotransferase I (KAT I) activity and kynurenic acid (KYNA) concentrations in human senile cataractous lenses and in experimentally induced cataracts in diabetic rats treated with streptozotocin (STZ).
METHODS:
KYNA levels and KAT I activity were investigated with HPLC and detected fluorimetrically in the nuclei of 91 human cataractous lenses collected during planned extracapsular extraction. The lenses were classified on the Lens Opacity Classification System III scale and compared with clear lenses regarding KYNA concentrations. Cataractous lenses from STZ-treated rats were compared with control lenses.
RESULTS:
KYNA concentration was 0.95 +/- 0.22 in human NC0 (nuclear color) control lenses, 0.8 +/- 0.72 in NC1, 1.18 +/- 0.88 in NC2, 1.31 +/- 0.70 in NC3, 1.78 +/- 0.92 in NC4, 8.80 +/- 8.28 (p < 0.05 vs. NC0) in NC5, and 14.0 +/- 11.1 (p < 0.05 vs. NC0) in NC6. A correlation was found between KYNA concentrations and the grade of cataract (r = 0.047, p < 0.001). KAT I activity in human cataracts was 0.44 +/- 0.16 pmol/mg protein- 1 hr- 1. Elevated KYNA concentrations in rat cataractous lenses were also observed (p < 0.05).
CONCLUSIONS:
KYNA levels are elevated in senile nuclear human cataracts and in cataractous lenses of rats with experimentally induced diabetes.
AuthorsTomasz Zarnowski, Robert Rejdak, Elzbieta Zielinska-Rzecka, Eberhart Zrenner, Paweł Grieb, Zbigniew Zagórski, Anselm Junemann, Waldemar A Turski
JournalCurrent eye research (Curr Eye Res) Vol. 32 Issue 1 Pg. 27-32 (Jan 2007) ISSN: 0271-3683 [Print] England
PMID17364732 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Streptozocin
  • Transaminases
  • kynurenine-oxoglutarate transaminase
  • Kynurenic Acid
Topics
  • Animals
  • Cataract (classification, metabolism)
  • Chromatography, High Pressure Liquid
  • Diabetes Mellitus, Experimental (metabolism)
  • Humans
  • Kynurenic Acid (metabolism)
  • Lens Nucleus, Crystalline (metabolism)
  • Male
  • Rats
  • Rats, Inbred BN
  • Streptozocin
  • Transaminases (metabolism)

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