INVERSE CORRELATION BETWEEN ENDOTHELIN-1-INDUCED PERIPHERAL MICROVASCULAR VASOCONSTRICTION AND BLOOD-PRESSURE IN GLAUCOMA PATIENTS

Background: The potent vasoconstrictor peptide endothelin-1 has been s hown to participate in the control of peripheral vascular tone and in the regulation of ocular perfusion, In glaucoma patients vasospasms an d arterial hypotension have been identified as risk factors for the pr ogression of glaucomatous damage, and the regulation of endothelin-1 r elease is disturbed in some of these patients. The aim of this study w as to assess the relationship between resting blood pressure and cutan eous vascular responsiveness to endothelin-1 and phenylephrine in pati ents with glaucoma and in matched controls. Methods: In 9 patients wit h primary open-angle glaucoma (POAG), 7 patients with normal tension g laucoma (NTG), and 16 age-and sex-matched controls, endothelin-1 and p henylephrine responses were assessed in the human forearm microcircula tion using laser Doppler flowmetry during intra-arterial drug administ ration. Blood pressure was measured intraarterially. Results: In contr ast to alpha(1)-adrenergic effects, endothelin-1 responses were invers ely correlated to both systolic (r(2) = 0.27, P = 0.05) and diastolic (r(2) = 0.54, P = 0.001) blood pressure in glaucoma patients, whereas there was no such correlation in controls, Patients with lower blood p ressure values were more sensitive to the vasoconstrictor effects of e ndothelin-1, Cutaneous responsiveness to endothelin-1 and phenylephrin e was similar in glaucoma patients and in controls. Conclusion: These- results reveal that glaucoma patients appear to have peripheral microv ascular abnormalities which are exhibited as altered responsiveness to endothelin-1. Thus, this study supports the hypothesis that endotheli n-1-related microvascular dysfunction may be involved in the pathogene sis of glaucomatous damage.