Endothelin 1 levels in the aqueous humor of dogs with glaucoma

Purpose: Endothelin 1 is a small peptide that is involved in regulation of intraocular pressure and modulation of ocular circulation. To investigate the role of endothelin 1 in canine glaucoma, the authors measured aqueous humor levels of endothelin 1 in healthy dogs and in dogs with hypertensive glaucoma. Methods: Aqueous humor samples were obtained with general anesthesia from the eyes of healthy dogs (n = 5) and dogs with hypertensive glaucoma (n = 10). Measurements, were made by enzyme immunoassay for endothelin 1. Results: The endothelin 1 aqueous humor range was 1. 12 - 3.63 pg/mL for healthy dogs and 1.97 - 14.97 pg/mL for glaucomatous dogs. The healthy and glaucomatous canine endothelin I aqueous levels (mean +/- SD) were 2.33 +/- 0.90 and 8.11 +/- 5.03 pg/mL, respectively. A two-way analysis of variance indicated that this difference was significant (P = 0.0084). The effect of age on endothelin 1 levels was not significant (P = 0.6283). The large variability found within the glaucomatous group could be explained by the degree of damage of the retina (P = 0.0006). There was no significant correlation between intraocular pressure and endothelin 1 aqueous humor levels within the glaucomatous group (P = 0.29). Conclusions: The aqueous humor of dogs with hypertensive glaucoma contains significantly higher levels of endothelin 1 than that of healthy dogs.