 |
|
Vitreous Amino Acid Concentrations in Patients With Glaucoma Undergoing Vitrectomy
Robert A. Honkanen, MD;
Sankar Baruah, MS;
M. Bridget Zimmerman, PhD;
Cheryl L. Khanna, MD;
Yaffa K. Weaver, MD;
Joanna Narkiewicz, MD;
Rafiq Waziri, MD;
Karen M. Gehrs, MD;
Thomas A. Weingeist, PhD, MD;
H. Culver Boldt, MD;
James C. Folk, MD;
Stephen R. Russell, MD;
Young H. Kwon, MD, PhD
Arch Ophthalmol. 2003;121:183-188.
Objective To measure vitreous concentrations of glutamate and other amino acids in patients with glaucoma undergoing vitrectomy.
Methods Undiluted vitreous samples were collected from patients undergoing vitrectomy at the University of Iowa (Iowa City) between 1997 and 1998 (n = 69). Vitreous concentrations of 16 amino acids, including glutamate, were determined using high-pressure liquid chromatography. Patients with a history of diabetes mellitus were excluded from the analysis. The study group consisted of those with a history of glaucoma (n = 8), and the control group included those with an epiretinal membrane and/or macular hole with no history of glaucoma (n = 17). Comparison of amino acid concentrations between the 2 groups was performed using a multifactor main effects model that adjusted for the effect of 10 selected covariates. Power analysis was done to determine the level of significant difference in amino acid concentrations.
Results The glaucoma group comprised vitreal specimens from patients with primary open-angle (n = 3) and angle-closure glaucomas that included aqueous misdirection (n = 2), uveitis with secondary angle-closure (n = 2), and Axenfeld Rieger syndrome (n = 1). Indications for vitrectomy in this group included epiretinal membrane, retinal detachment, aqueous misdirection, and uveitis. The control group included specimens from patients with a macular hole (n = 11) and epiretinal membrane (n = 7), with 1 eye having both. Surgical indications in controls were macular hole, retinal detachment, and epiretinal membrane. The mean ± SD levels of vitreous glutamate, glycine,  -aminobutyric acid, and alanine were 6.1 ± 2.4, 16.3 ± 7.5, 0.8 ± 0.3, and 260.5 ± 101.9 µM, respectively, in glaucoma and 5.2 ± 2.3, 8.5 ± 2.5, 0.6 ± 0.2, and 159.5 ± 54.9 µM in controls (P>.05 for all). None of the 16 amino acid concentrations measured showed a statistically significant difference between glaucoma and controls (P values between .06 and >.99). A power analysis indicated that a 1.8-fold elevation in the glutamate level was needed to reach significance.
Main Outcome Measures Vitreous amino acid concentrations.
Conclusions None of the 16 amino acids measured, including glutamate, were significantly elevated in the vitreous of glaucomatous eyes compared with controls. Our results are not consistent with the simple hypothesis of glutamate excitotoxicity in glaucoma. Instead, our findings indicate the dynamic nature of extracellular glutamate, whose concentration is dependent on complex mechanisms not yet fully understood. Further studies are needed to fully elucidate the role of glutamate in the pathogenesis of glaucoma.
From the Departments of Ophthalmology and Visual Sciences (Drs Honkanen, Khanna, Weaver, Narkiewicz, Gehrs, Weingeist, Boldt, Folk, Russell, and Kwon) and Psychiatry (Dr Waziri and Mr Baruah); and the Department of Biostatistics, College of Public Health (Dr Zimmerman), University of Iowa, Iowa City. Authors have no relevant financial interest in this article.
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
|
Quantification of Retinal Transneuronal Degeneration in Human Glaucoma: A Novel Multiphoton-DAPI Approach
Lei et al.
IOVS 2008;49:1940-1945.
ABSTRACT
| FULL TEXT
CaMKII{alpha}B Mediates a Survival Response in Retinal Ganglion Cells Subjected to a Glutamate Stimulus
Fan et al.
IOVS 2007;48:3854-3863.
ABSTRACT
| FULL TEXT
Proteomic Identification of Oxidatively Modified Retinal Proteins in a Chronic Pressure-Induced Rat Model of Glaucoma
Tezel et al.
IOVS 2005;46:3177-3187.
ABSTRACT
| FULL TEXT
Vitreous Glutamate Concentration and Axon Loss in Monkeys With Experimental Glaucoma
Wamsley et al.
Arch Ophthalmol 2005;123:64-70.
ABSTRACT
| FULL TEXT
Susceptibilities to and Mechanisms of Excitotoxic Cell Death of Adult Mouse Inner Retinal Neurons in Dissociated Culture
Luo et al.
IOVS 2004;45:4576-4582.
ABSTRACT
| FULL TEXT
Glutamate-Induced Glutamine Synthetase Expression in Retinal Muller Cells after Short-term Ocular Hypertension in the Rat
Shen et al.
IOVS 2004;45:3107-3112.
ABSTRACT
| FULL TEXT
Efficacy and Safety of Memantine Treatment for Reduction of Changes Associated with Experimental Glaucoma in Monkey, I: Functional Measures
Hare et al.
IOVS 2004;45:2625-2639.
ABSTRACT
| FULL TEXT
|
