The Role of Nitric Oxide on EDTA-induced Vasoconstriction in Isolated Rabbit Aorta

一氧化氮對於高濃度EDTA所致離體主動脈血管收縮之影響

蔡輝彥(Huei-Yann Tsai) ； 朱秋玲(Chiou-Ling Chu) ； 謝文聰(Wen-Tsong Hsieh) ； 陳玉芳(Yuh-Fung Chen) ； 李正淳(Cheng-Chieh Lee) ； 蔡長海(Chang-Hai Tsai)

《Mid-Taiwan Journal of Medicine》 6卷1期 (2001/03) Pp. 22-29

https://doi.org/10.6558/MTJM.2001.6(1).4

摘要

背景臨床上EDTA用於治療粥狀、動脈硬化及鉛中毒。但使用劑量大於5g/infusion (1000 mL)，會有致命性的腎毒性。在離體實驗中，EDTA用於盤合鈣離子5，大多小於1mM。但有些學者，也有使用大用20 mM者。而此高濃度EDTA是否會對平滑肌產生何種作用，並未討論。在我們先前的實驗中曾探討高濃度EDTA與鎂離子和鈣離子之關係。本實驗我們試著探討EDTA與內源性或外源性的一氧化氮之何者關係較密切。
方法本實驗根據Furchgott所述之方法，採取兔子主動脈平滑肌當樣本。血管條片兩端以組棉線綁好，置於含10毫升Kreb's Ringer氏液之Magnus氏器官槽(organ bath)內，槽內並通入95%O2和5%O2氣體，器官槽維持在37℃±0.5℃。血管 樣本懸掛好之後逐漸調整張力至2.0公克，待平衡90分鐘至120分鐘，血管張力穩定後進 行藥物測試。
結果 EDTA在濃度大於4 mM以上，對於血管具有顯著的收縮作用，並呈現濃度依存性(dose-dependent)：且不論內皮存在與否，EDTA能產生收縮作用，但是去除內皮後，EDTA之收縮作用稍微降低。外源性的一氧化氮(NO)，sodium nitroprusside。(1×10-5M)對於EDTA所致的血管收縮作用具有明顯的抑制作用：當無內皮存在時其抑制率約113.7%，當有內皮存在時其抑制率約84.4%。而NO的前軀物，L-arginine (1×1O-4M)與NO合成霉抑制劑. L-NAME (1×10吉M)對於EDTA所致的血管收縮的抑制作用並不明顯。但Cyclic GMP的促進劑， 8-Br cG MP (1×10-4M)可明顯抑制 EDTA所致的血管收縮作用。
結論在離體血管中，EDTA濃度在大於4 mM以上，對於血管具有顯著的收縮作用， 並呈現濃度依存性(dose-dependent)；由結果顯現內源性一氧化氮(endogenous NO)參與EDTA所致的血管收縮作用關係並不密切。

關鍵字

EDTA ； 氧化氮 ； 血管收縮作用

並列摘要

Background. The chelating agent, ethylenediamine tetraacetic acid (EDTA) is used to treat atherosclerosis. However, it is known to lead to intoxication at doses of more than5g/infusion (1000 mL), and to cause fatal renal toxicity. In vitro studies, the concentration of EDTA used to chelate Ca2+ is usually less than 1 mM. Some scholars have used more than 20 mM EDTA to test for increased Ca2+-chelating activity, but have not discussed the effect of high concentrations of EDTA on smooth muscles or its influence upon other ions. In this study, we attempted to investigate whether EDTA (5mM)-induced vasoconstriction is related to exogenous or endogenous nitric oxide (NO).
Methods. This experiment was based on Furchgott's treatment of rabbit aortic smooth muscles. Strips of aorta were carefully tightened with silk threads, and placed in 10 ml of Kreb's Ringer solution with air containing 95% of O2 and5% of CO2. The temperature was kept at 37±5℃ in the organ bath and the pH at 7.3-7.4. The tension was gradually adjusted to 2.0 g. A 90-120 min waiting period was allowed for the apparatus to reach stability before testing.
Results. EDTA evoked vasoconstriction when the concentration was higher than 4 mM. The exogenous NO donor, sodium nitroprusside (SNP) markedly inhibited EDTA (5mM)-induced vasoconstriction. The inhibition rate of SNP on EDTA-induced vasoconstriction was 113.7% when the endothelium was absent and 84.4% when present. L-arginine (NO precursor; 1 X 10-4 M) and the inhibitor of NO synthase, Nω-nitro-L-arginine methyl ester (1 X 10-5M), had little effect. However, the cGMP analog, 8-bromoguanosine 3', 5’-cyclic monophosphate (l x 10-5M), inhibited EDTA-induced vasoconstriction. Conclusions. When the concentration was greater than 4 mM, EDTA induced vasoconstriction, reaching its peak effect at a concentration of 60 mM in isolated rabbit aorta. Furthermore, the vasoconstriction induced by5mM EDTA was not directly related to the inhibition of endogenous NO.

並列關鍵字

EDTA ； nitric oxide ； vasoconstriction