Endothelin and its potential role in glaucoma.

Endothelin is a potent vasoactive peptide occurring in 3 isotypes, ET-1, ET-2, and ET-3. Through its two main receptors, endothelin A and endothelin B, it is responsible for a variety of physiological functions, primarily blood flow control. Recent evidence from both human and experimental optic neuropathies shows involvement of endothelin and upregulation of its receptors (principally endothelin B). Experimental studies have shown that chronic ET-1 administration to the optic nerve immediately behind the globe causes neuronal damage, activation of astrocytes, the major glial cell in the anterior optic nerve, and upregulation of endothelin B receptors. This review outlines the ubiquitous role of endothelin and its potential involvement in glaucoma.