Quantification of an endogenous neuroprotectant kynurenic acid in the human and rabbit vitreous body
T. Zarnowski1, R. Rejdak2, Z. Zagórski1, A. G. M. Jünemann3, T. Kocki2, W. A. Turski2
Aim: Kynurenic acid (KYNA), tryptophan metabolite, NMDA antagonist displays potent neuroprotective effect in the brain and in the retina. This study was designed to examine its presence in the human and rabbit vitreous body and to validate its possible intraocular origin.
Material and Methods: KYNA levels were determined employing HPLC technique in the vitreous body of 4 human cadaveric eyes and 19 eyes of Albino rabbits. KYNA concentration was also measured in 21 rabbits, 2, 24 and 48 hours following intravitreal injection of 10 mmol aminooxyacetic acid (AOAA), KYNA synthesis inhibitor. Contralateral eye was injected with saline (control group). Statistical analysis was performed using Students t-test.
Results: Mean (± SD) KYNA concentration in the human vitreous body was 33,1 ± 6,2 pmol/ml. Mean (± SD) KYNA concentration in the rabbit vitreous body was 22,3 ± 3,9 pmol/ml. Intravitreal administration of AOAA diminished KYNA production by 10% (NS) - 2 hours, 48% (P<0.001 vs. saline treated group) - 24 hours and 25 % (P<0.05) - 48 hours, following the treatment.
Conclusions: KYNA, a putative endogenous neuroprotectant has been quantified in the human and rabbit vitreous body. It is further concluded that AOAA decreases intravitreal concentration of KYNA thus providing evidence of its intraocular synthesis.
1Tadeusz Krwawicz Chair of Ophthalmology and 1st Eye Hospital, Medical University School, Lublin, Poland