Endothelin-1, nitric oxide, and glutamate in the normal and glaucomatous dog eye.

Purpose  To document differences in the levels of the endothelin-1 peptide, nitric oxide, and glutamate in aqueous humor and vitreous in the dog eye with spontaneous glaucoma compared to the normal dog eye. Methods  Samples of aqueous humor and vitreous from enucleated normal eyes (n = 21) of 14 dogs and glaucomatous eyes (n = 8) of eight dogs were collected. Levels of endothelin-1, nitric oxide, and glutamate were measured by enzyme immunoassay. Results  Endothelin-1 aqueous humor levels (mean ± SD) increased significantly from 3.05 (± 1.66) pg/mL for the normal eyes to 6.22 (± 2.83) pg/mL for the glaucomatous eyes (P = 0.0054). The increase in vitreous from 1.83 (± 1.66) pg/mL for the normal eyes to 2.86 (± 1.31) pg/mL for the glaucomatous eyes was not significant (P = 0.0840). Nitric oxide levels (mean ± SD) increased significantly in aqueous humor from 4.12 (± 2.64) µM for the normal eyes to 12.95 (± 14.42) µM for the glaucomatous eyes (P = 0.0141). The vitreous levels increased from 4.86 (± 3.92) µM for the normal eyes to 15.33 (± 16.22) µM for the glaucomatous eyes (P = 0.0179). Glutamate levels (mean ± SD) decreased nonsignificantly in aqueous humor from 2.35 (± 3.84) µM for the normal eyes to 1.61 (± 0.74) µM for the glaucomatous eyes (P = 0.9377) and in vitreous from 1.37 (± 1.89) µM for the normal eyes to 1.02 (± 1.11) µM for the glaucomatous eyes (P = 0.3303). Conclusion  Endothelin-1 and nitric oxide increased in aqueous humor and vitreous of dogs with spontaneous glaucoma while the changes in glutamate varied.