Endothelin-B Receptors on Suprachoroidal Melanocytes Mediate an Endothelin-1–Induced Increase in the Intracellular Calcium Concentration of Rabbit Ocular Suprachoroidal Tissue

Abstract

The physiological properties of endothelin-1 in ocular choroidal melanocytes are not well-known, although endothelin-1 increases the intracellular calcium concentration through endothelin-B receptors in skin melanocytes. We studied the effect of endothelin-1 on choroidal melanocytes in rabbit ocular suprachoroidal tissue. Fura-2 microfluorophotometry indicated that endothelin-1 and endothelin-B receptor selective agonists, endothelin-3 and BQ3020, increased the intracellular calcium concentration of the tissue. Endothelin-B receptor selective antagonist BQ788 blunted the response. Immuno-electron microscopy showed that endothelin-B receptor-like immunoreactivity was located only on melanocytes. These results indicate that endothelin-1 increases intracellular calcium concentration in rabbit suprachoroidal tissue via endothelin-B receptors on melanocytes.

KEYWORDS:

• endothelin-1
• endothelin-B receptor
• fura-2 microfluorophotometry
• immuno-electron microscopy
• suprachoroidal melanocytes