title: Elevated concentrations of kynurenic acid, a tryptophan derivative, in dense nuclear cataracts.
abstract: OBJECTIVE
  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.
authors: Tadeusz Krwawicz Chair of Ophthalmology and 1st Eye Hospital, Medical University of Lublin. Lublin, Poland. zarnowskit@poczta.onet.pl
authors: Tomasz
authors: T
authors: Zarnowski
authors: Robert
authors: R
authors: Rejdak
authors: Elzbieta
authors: E
authors: Zielinska-Rzecka
authors: Eberhart
authors: E
authors: Zrenner
authors: Paweł
authors: P
authors: Grieb
authors: Zbigniew
authors: Z
authors: Zagórski
authors: Anselm
authors: A
authors: Junemann
authors: Waldemar A
authors: WA
authors: Turski
mesh_terms: D000818:Animals; D002386:Cataract / Q000145:classification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D006801:Humans; D007736:Kynurenic Acid / Q000378:metabolism*; D007907:Lens Nucleus, Crystalline / Q000378:metabolism*; D008297:Male; D051381:Rats; D011914:Rats, Inbred BN; D013311:Streptozocin; D000637:Transaminases / Q000378:metabolism
chemical_list: D013311:Streptozocin; D000637:Transaminases; C021481:kynurenine-oxoglutarate transaminase; D007736:Kynurenic Acid