Immunoreactive endothelin distribution in ocular tissues.

PURPOSE To study the distribution of the endothelins in the eye using ocular tissues of human, rat, and porcine origin. METHODS Extracts of ocular tissues were examined for immunoreactivity to endothelin 1 and 3 and pro-endothelin 1 using radioimmunoassay. Characterization of immunoreactivity was verified using high-performance liquid chromatography. RESULTS Immunoreactivity to endothelin 1 and endothelin 3 was found in all ocular tissues except the cornea, which contained no immunoreactivity to endothelin 3. Highest levels were found in the choroid, although species-related differences were present. Immunoreactivity to endothelin 3 was generally twofold to threefold higher than immunoreactivity to endothelin 1. The majority of endothelin-like-immunoreactivity in the retina was blood vessel-associated. High-pressure liquid chromatography (HPLC) confirmed that immunoreactive endothelin 1 and endothelin 3 in the tissue extracts eluted in identical positions to their respective standard synthetic peptides. CONCLUSIONS The endothelins are abundantly distributed in the eye. Endothelin 1 is present in its mature, 21 amino acid form, and only minimal amounts of the precursor pro-endothelin is found in ocular tissues. The wide distribution patterns point to complex roles for these peptides in blood vessel physiology and in such other functions as regulation of aqueous outflow, and in neurotransmission or modulation.