エンドセリンの内眼筋におよぼす影響

Effects of endothelins on intrinsic ocular muscles

　30Gの注射針を用いて白色家兎24羽の片眼硝子体中に各濃度のエンドセリン-10.1mlを，他眼対照眼にオペガード^®MA0.1mlを投与した。エンドセリン-1投与眼は有意に縮瞳し，近視化した。縮瞳作用に用量反応関係が成立し，10^-6Mが実験に最適の濃度であると判明した。エンドセリン-1による縮瞳はアトロピン前処置の影響を受けなかったため，副交感神経系の関与が否定された。局所のエンドセリンレセプターヘの直接作用のほかに，ジクロフェナクナトリウムの点眼投与による縮瞳抑制がみられたことから，プロスタグランディンやvasoactive intestinal polypeptideなどの炎症起因性物質がエンドセリン-1によって誘発放出されたためと思われた。

We investigated the effects of endothelins, a vasoconstrictive peptide derived from the vascular endothelium, on the intrinsic ocular muscles of experimental animals. Twenty-four albino rabbits underwent intravitreal injection of endothelin-1 (0.1 ml) of 10^-5M, 10^-6M, and 10^-7M concentrations on the unilateral eyes and Opegard^® MA 0.1 ml on the other eyes as control. Fine needles of 30G were adopted. We measured the pupillary horizontal diameter every 30 to 60 minutes by a Haab papillometer and refraction by conventional retinoscopy. Endothelin-1 caused a significant miosis 30 minutes after injection which lasted for 720 to 840minutes. The contralateral control eyes showed absent or minimum miotic change. A dose-response ralation was found in this pupillary change. Refraction became myopic 30 minutes after the manipulation and continued for 150 minutes. Topical diclofenac sodium 0.1% fully inhibited the endothelium-induced miosis. Atropine sulfate 1% did not suppress the effect of the endothelin on the intrinsic ocular muscles. From the results we thought that the effect of endothelin-1 on intrinsic ocular muscles may be mediated by local arachidonic acid metabolites, prostaglandins or vasoactive intestinal polypeptides, and that the parasympathetic nerve system may hardly be involved in this mechanism.