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RA Honkanen, S Baruah, MB Zimmerman, CL Khanna, KM Gehrs, TA Weingeist, HC Boldt, SR Russell, JC Folk, YH Kwon; Vitreous Amino Acid Concentrations in Patients with Proliferative Diabetic Retinopathy Undergoing Vitrectomy . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3470.
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Purpose:Evaluate vitreous amino acid levels in patients with proliferative diabetic retinopathy (PDR) undergoing vitrectomy. Methods:We collected undiluted vitreous samples in 69 eyes of 69 consecutive patients undergoing vitrectomy from 7/97 to 4/98. Of these, 21 specimens from eyes with PDR (20 with vitreous hemorrhage) comprised the study group. For controls, 17 specimens from eyes of non-diabetic patients who underwent vitrectomy for either macular hole or epiretinal membrane (no vitreous hemorrhage) were selected. The remaining 24 eyes with multiple ocular conditions confounding categorization were excluded from analysis. Concentrations of 16 amino acids were analyzed using HPLC. Statistical comparisons of relative amino acid levels were performed using multi-factor main effects model that adjusted for the effect of selected covariates. P-values were adjusted by the number of amino acids using Bonferroni's method; adjusted p-values < 0.05 were considered significant. Results:The vitreous levels of Ala, Asn, Gly, His, Ile, Leu, Lys, Met, Phe, Ser, and Thr were significantly elevated in PDR eyes compared to controls. The Asp, GABA, Glu, Gln, and Tyr levels were not significantly elevated in PDR eyes. In particular, Glu and GABA concentrations (in µM) were 6.9 2.1 and 1.1 0.7 in PDR and 5.22.3 and 0.60.2 in controls respectively (p = 0.45 and 0.12 respectively). Conclusion:Elevated amino acid concentrations in PDR eyes with vitreous hemorrhage probably reflect relatively higher concentrations of these amino acids in plasma (compared to vitreous). Interestingly, the levels of neurotransmitter amino acids (glutamate and GABA) were similar between PDR and controls, suggesting selective uptake or metabolism of these important amino acids from the vitreous following hemorrhage.
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