Altered Endothelin-1 Vasoreactivity in Patients with Untreated Normal-Pressure Glaucoma

Vasospasm, resulting from a generalized dysfunction in the vascular endothelium, is implicated in the development of normal-pressure glaucoma (NPG). Impaired endothelium-derived nitric oxide activity and abnormalities of the endothelin system suggest systemic endothelial cell dysfunction in patients with NPG. Endothelin (ET)-1 vasoreactivity was assessed in the peripheral circulation of patients with NPG. Forearm blood flow was measured using venous occlusion plethysmography in eight patients with untreated NPG and eight age- and sex-matched healthy volunteers during intra-arterial infusion of ET-1 (5 pmol/min) and, on a separate occasion, to BQ123, a selective endothelin-A receptor antagonist, (100 nmol/min). Blood pressure and heart rate were measured in the noninfused arm, and plasma ET-1 concentrations were measured using a radioimmunoassay. Forearm blood flow fell during infusion of ET-1 (P