VITREOUS BODY GLUTAMATE CONCENTRATION IN DOGS WITH GLAUCOMA

Objective-To analyze the vitreal amino acid concentrations in dogs wit h breed-related primary glaucoma to determine whether excitotoxic amin o acids associated with retinal ganglion cell death in other species w ere present in affected dogs. Samples-11 normal control and 10 glaucom atous canine eyes. Procedure-Amino acid analyses were performed by hig h-pressure liquid chromatography in masked manner. Results-Eyes from d ogs with primary glaucoma had significantly high vitreal glutamate con centration, compared with values for eyes of clinically normal control dogs. Mean (+/- SD) glutamate concentrations were 31.7 +/- 12.4 and 6 .9 +/- 6.3 mu M in glaucomatous and normal eyes, respectively (P < 0.0 001). Eyes from dogs with glaucoma also had lower vitreal glycine (37. 0 +/- 170 vs 59.4 +/- 28.2 mu M; P < 0.043) and higher of vitreal tryp tophan (39.0 +/- 22.8 vs 17.5 +/- 11.2 mu M; P < 0.012) concentrations , compared with values for normal eyes. Conclusion-Glutamate concentra tion potentially toxic to retinal ganglion cells is associated with th e pathogenesis of primary glaucoma in dogs. Increased glutamate concen tration provides evidence of an ischemic mechanism for retinal ganglio n cell death and optic nerve atrophy in dogs with glaucoma. Clinical R elevance-The emphasis on reduction and normalization of high intraocul ar pressure as the primary focus of treatment for glaucoma in dogs sho uld be augmented by other therapeutic approaches.