The endothelium-derived hyperpolarising factor (EDHF) in isolated bovine choroidal arteries

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• 作者：Christophe Delaey ; Koen Boussery ; Joke Breyne ; Bert Vanheel ; Johan Van de Voorde
• 关键词：choroid ; choroidal arteries ; EDHF ; hyperpolarisation ; vasodilation
• 刊名：Experimental Eye Research
• 出版年：2007
• 出版时间：June 2007
• 年：2007
• 卷：84
• 期：6
• 页码：1067-1073
• 全文大小：180 K

文摘

The present study reports of an endothelium-dependent and NO- and prostanoid-independent relaxation in isolated choroidal arteries, and evaluates the hypothesis of an endothelium-derived hyperpolarising factor (EDHF) playing a role in the choroidal circulation. Choroidal arteries were isolated from bovine eyes and mounted in a small vessel wire-myograph for isometric tension recording. Concentration-response curves for acetylcholine (0.1 nM–10 μM) were constructed in isolated choroidal arteries contracted with 10 μM norepinephrine. Acetylcholine induced a concentration-dependent relaxation in the choroidal arteries. The presence of the NO-synthase inhibitor L-NA and the cyclo-oxygenase inhibitor indomethacin only had a limited effect on this relaxation. All further experiments were performed in the presence of L-NA and indomethacin, in order to study the NO- and prostanoid-independent part of the acetylcholine-relaxations. Both removal of the vascular endothelium or the presence of an increased K⁺ concentration in the organ bath abolished the NO- and prostanoid-independent part of the acetylcholine-relaxations. The presence of TEA, a rather non-specific K⁺ channel blocker, significantly reduced the acetylcholine-relaxations. Simultaneous application of apamin (an inhibitor of small-conductance Ca²⁺-activated K⁺ channels) and charybdotoxin (an inhibitor of intermediate- and large-conductance Ca²⁺-activated K⁺ channels) abolished the acetylcholine-induced relaxation and even resulted in a concentration-dependent contraction. Transmembrane potential recordings in isolated choroidal arteries revealed a clear membrane hyperpolarisation in the vascular smooth muscle cells of isolated choroidal arteries. It was therefore concluded that the acetylcholine-induced relaxation of choroidal arteries in the presence of NO-synthase and cyclo-oxygenase inhibitors is mediated by an endothelium-derived hyperpolarising factor. This EDHF seems to be of more importance than endothelium-derived NO or prostanoids.