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 o f ocular tissues were examined for immunoreactivity to endothelin 1 an d 3 and pro-endothelin 1 using radioimmunoassay. Characterization of i mmunoreactivity was verified using high-performance liquid chromatogra phy. Results. Immunoreactivity to endothelin 1 and endothelin 3 was fo und in all ocular tissues except the cornea, which contained no immuno reactivity 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 immunorea ctivity to endothelin 1. The majority of endothelin-like-immunoreactiv ity in the retina was blood vessel-associated. High-pressure liquid ch romatography (HPLC) confirmed that immunoreactive endothelin 1 and end othelin 3 in the tissue extracts eluted in identical positions to thei r 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 patt erns point to complex roles for these peptides in blood vessel physiol ogy and in such other functions as regulation of aqueous outflow, and in neurotransmission or modulation.