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Abstract #5178 Published in IGR 1-2
Role of endothelium-derived vasodilators and K+ channels in ischemic vasodilation of guinea-pig choroidal arterioles
Tamai K; Suzuki H; Shirai S; Ogura YCurrent Eye Research 1999; 19: 182-187
PURPOSE: To assess the roles of endothelium-derived vasodilators and K+ channels on metabolic ischemic-induced vasodilatation from diameter changes in choroidal arterioles of the guinea-pig. METHODS: The choroid was isolated from the guinea-pig eyeball, pinned flat on a silicone rubber plate, and superfused with oxygenated warmed (35?C) Krebs solution. Diameters of choroidal arterioles were measured using video microscopy and a computer program for analysis. Vasodilatory effects were examined after the choroid was exposed to glucose-free/NaCN solutions for 10 minutes. The effects of N -nitro-L-arginine (nitroarginine), indomethacin, and K+ channel inhibitors (glibenclamide (Glib) and charybdotoxin (ChTX)) on ischemic vasodilatation were assessed. RESULTS: Reversible vasodilation was observed when the choroid was exposed to glucose-free/NaCN (10-3M) solutions. Nitroarginine (10-4M), Glib (2x10-5M) and ChTX (10-7M) significantly inhibited glucose-free/NaCN (10-3M)-induced vasodilatation by 47%, 62%, and 24%, respectively. No significant inhibitory effect was observed with indomethacin (10-5M). Simultaneous application of Glib and ChTX reduced vasodilatation by 77%. When Glib and ChTX were added together to initroarginine, dilation was reduced by 86%. With high K+ ([K]o=47.2 mM) Krebs solution, ischemia caused a slight vasodilatation (11%), which was significantly inhibited by nitroarginine. CONCLUSIONS: In guinea-pig choroidal arterioles, glucose-free/NaCN-induced ischemic vasodilatation was mainly mediated by NO and KATP channels. A part of NO-mediated vasodilatation was induced independent of the opening of K+ channels.
K. Tamai, Department of Ophthalmology, Nagoya City University Medical School, Nagoya; Japan
Classification:
1.3 Pathogenesis (Part of: 1 General aspects)