Elevated concentrations of kynurenic acid, a tryptophan derivative, in dense nuclear cataracts.
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.
Zarnowski
Tomasz
T
Tadeusz Krwawicz Chair of Ophthalmology and 1st Eye Hospital, Medical University of Lublin. Lublin, Poland. zarnowskit@poczta.onet.pl
Rejdak
Robert
R
Zielinska-Rzecka
Elzbieta
E
Zrenner
Eberhart
E
Grieb
Paweł
P
Zagórski
Zbigniew
Z
Junemann
Anselm
A
Turski
Waldemar A
WA
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
D013311:Streptozocin; D000637:Transaminases; C021481:kynurenine-oxoglutarate transaminase; D007736:Kynurenic Acid