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Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat.
Invest Ophthalmol Vis Sci. 2002 Jul; 43(7):2236-43.IO

Abstract

PURPOSE

High levels of glutamate can be toxic to retinal ganglion cells. Effective buffering of extracellular glutamate by retinal glutamate transporters is therefore important. This study was conducted to investigate whether glutamate transporter changes occur with two models of optic nerve injury in the rat.

METHODS

Glaucoma was induced in one eye of 35 adult Wistar rats by translimbal diode laser treatment to the trabecular meshwork. Twenty-five more rats underwent unilateral optic nerve transection. Two glutamate transporters, GLAST (EAAT-1) and GLT-1 (EAAT-2), were studied by immunohistochemistry and quantitative Western blot analysis. Treated and control eyes were compared 3 days and 1, 4, and 6 weeks after injury. Optic nerve damage was assessed semiquantitatively in epoxy-embedded optic nerve cross sections.

RESULTS

Trabecular laser treatment resulted in moderate intraocular pressure (IOP) elevation in all animals. After 1 to 6 weeks of experimental glaucoma, all treated eyes had significant optic nerve damage. Glutamate transporter changes were not detected by immunohistochemistry. Western blot analysis demonstrated significantly reduced GLT-1 in glaucomatous eyes compared with control eyes at 3 days (29.3% +/- 6.7%, P = 0.01), 1 week (55.5% +/- 13.6%, P = 0.02), 4 weeks (27.2% +/- 10.1%, P = 0.05), and 6 weeks (38.1% +/- 7.9%, P = 0.01; mean reduction +/- SEM, paired t-tests, n = 5 animals per group, four duplicate Western blot analyses per eye). The magnitude of the reduction in GLT-1 correlated significantly with mean IOP in the glaucomatous eye (r(2) = 0.31, P = 0.01, linear regression). GLAST was significantly reduced (33.8% +/- 8.1%, mean +/- SEM) after 4 weeks of elevated IOP (P = 0.01, paired t-test, n = 5 animals per group). In contrast to glaucoma, optic nerve transection resulted in an increase in GLT-1 compared with the control eye (P = 0.01, paired t-test, n = 15 animals). There was no significant change in GLAST after transection.

CONCLUSIONS

GLT-1 and GLAST were significantly reduced in an experimental rat glaucoma model, a response that was not found after optic nerve transection. Reductions in GLT-1 and GLAST may increase the potential for glutamate-induced injury to RGC in glaucoma.

Authors+Show Affiliations

Glaucoma Research Laboratory, Wilmer Eye Institute, Johns Hopkins University, 600 North Wolfe Street, Baltimore, MD 21287, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

12091422

Citation

Martin, Keith R G., et al. "Retinal Glutamate Transporter Changes in Experimental Glaucoma and After Optic Nerve Transection in the Rat." Investigative Ophthalmology & Visual Science, vol. 43, no. 7, 2002, pp. 2236-43.
Martin KR, Levkovitch-Verbin H, Valenta D, et al. Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat. Invest Ophthalmol Vis Sci. 2002;43(7):2236-43.
Martin, K. R., Levkovitch-Verbin, H., Valenta, D., Baumrind, L., Pease, M. E., & Quigley, H. A. (2002). Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat. Investigative Ophthalmology & Visual Science, 43(7), 2236-43.
Martin KR, et al. Retinal Glutamate Transporter Changes in Experimental Glaucoma and After Optic Nerve Transection in the Rat. Invest Ophthalmol Vis Sci. 2002;43(7):2236-43. PubMed PMID: 12091422.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat. AU - Martin,Keith R G, AU - Levkovitch-Verbin,Hana, AU - Valenta,Danielle, AU - Baumrind,Lisa, AU - Pease,Mary Ellen, AU - Quigley,Harry A, PY - 2002/7/2/pubmed PY - 2002/7/16/medline PY - 2002/7/2/entrez SP - 2236 EP - 43 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 43 IS - 7 N2 - PURPOSE: High levels of glutamate can be toxic to retinal ganglion cells. Effective buffering of extracellular glutamate by retinal glutamate transporters is therefore important. This study was conducted to investigate whether glutamate transporter changes occur with two models of optic nerve injury in the rat. METHODS: Glaucoma was induced in one eye of 35 adult Wistar rats by translimbal diode laser treatment to the trabecular meshwork. Twenty-five more rats underwent unilateral optic nerve transection. Two glutamate transporters, GLAST (EAAT-1) and GLT-1 (EAAT-2), were studied by immunohistochemistry and quantitative Western blot analysis. Treated and control eyes were compared 3 days and 1, 4, and 6 weeks after injury. Optic nerve damage was assessed semiquantitatively in epoxy-embedded optic nerve cross sections. RESULTS: Trabecular laser treatment resulted in moderate intraocular pressure (IOP) elevation in all animals. After 1 to 6 weeks of experimental glaucoma, all treated eyes had significant optic nerve damage. Glutamate transporter changes were not detected by immunohistochemistry. Western blot analysis demonstrated significantly reduced GLT-1 in glaucomatous eyes compared with control eyes at 3 days (29.3% +/- 6.7%, P = 0.01), 1 week (55.5% +/- 13.6%, P = 0.02), 4 weeks (27.2% +/- 10.1%, P = 0.05), and 6 weeks (38.1% +/- 7.9%, P = 0.01; mean reduction +/- SEM, paired t-tests, n = 5 animals per group, four duplicate Western blot analyses per eye). The magnitude of the reduction in GLT-1 correlated significantly with mean IOP in the glaucomatous eye (r(2) = 0.31, P = 0.01, linear regression). GLAST was significantly reduced (33.8% +/- 8.1%, mean +/- SEM) after 4 weeks of elevated IOP (P = 0.01, paired t-test, n = 5 animals per group). In contrast to glaucoma, optic nerve transection resulted in an increase in GLT-1 compared with the control eye (P = 0.01, paired t-test, n = 15 animals). There was no significant change in GLAST after transection. CONCLUSIONS: GLT-1 and GLAST were significantly reduced in an experimental rat glaucoma model, a response that was not found after optic nerve transection. Reductions in GLT-1 and GLAST may increase the potential for glutamate-induced injury to RGC in glaucoma. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/12091422/Retinal_glutamate_transporter_changes_in_experimental_glaucoma_and_after_optic_nerve_transection_in_the_rat_ L2 - https://iovs.arvojournals.org/article.aspx?volume=43&issue=7&page=2236 DB - PRIME DP - Unbound Medicine ER -