Plasma and aqueous humor endothelin levels in primary open-angle glaucoma

Purpose: Endothelins (ET) have some effects on the regulation of aqueous humor dynamics. To investigate their possible role in glaucoma, we measured plasma and aqueous humor ET levels in patients with and without primary open-angle glaucoma. Methods: Plasma and aqueous humor samples were obtained from 31 patients with primary open-angle glaucoma and 24 patients without glaucoma. Measurements were made by radioimmunoassay (RIA) for ETs with the following cross-reactivities: ET-1, ET-2, and big ET-1, 100%; and ET-3, 70%. Results: The ages (mean ± SD) of the patients with primary open-angle glaucoma (72.3 ± 10 years) and normal subjects (72.8 ± 8 years) were similar (p = 0.92). There was no significant difference between plasma ET levels of the two groups (p = 0.07). However, aqueous humor ET levels (mean ± SD) were higher in the primary open-angle glaucoma group (44.26 ± 2.6 pg ml^-1) than in normal subjects (42.17 ± 1.6 pg ml^-1) (p = 0.001). The ratios of corresponding aqueous humor to plasma levels of ETs were ~ 10% higher in the primary open-angle glaucoma group (3.76) than in normal subjects (3.41) (p = 0.0002). Conclusions: The small increase in aqueous humor endothelin levels in patients with primary open-angle glaucoma versus controls of similar age may be relevant to the understanding of the various roles of ETs in aqueous humor dynamics in these patients.