花生四烯酸對人類血小板所產生氫氧自由基之探討 The
Mechanisms Involved in Arachidonic Acid-Induced Hydroxyl
Radical Formation in Human Platelets.
中文摘要
過去由 Daljeet et al 等人使用 14CO2 quantification 技術研究指出，花生四
烯酸能使血小板產生氫氧自由基，但其使用的是間接的方法測定自由基的含量。
因此本實驗的目的是以直接的方式─電子順磁共振儀 (ESR) 測定花生四烯酸
是否能使血小板產生氫氧自由基，並進一步探討其詳細機制。在初步實驗中，於
電子順磁共振 (ESR) 中，以 DMPO (5,5-dimethyl-1-pyrrolin-N-oxide)當
補捉自由基試劑，我們發現低濃度花生四烯酸會促進血小板產生氫氧自由基。花
生四烯酸的代謝有三種途徑可能產生氫氧自由基，即 Lipoxygenase，
Cyclooxygenase，NADPH oxidase 之路徑。本實驗進一步探討發現低濃度花
生四烯酸在血小板中產生的氫氧自由基是經由 12-lipoxygenase pathway 而
來的。除此之外，本實驗還以此一系統測試一些天然抗氧化物例如：resveratrol,
rutin, quercetin，及 lycopene 等。研究顯示能有效地清除低濃度花生四烯酸
促進血小板產生的氫氧自由基。然而我們發現當 12-lipoxygenase 被抑制時，
會產生另一種自由基為 g = 2.006 自由基，此自由基的產生是因高濃度的
peroxides 使得中間自由基產物的累積，進而產生自我的摧毀現象。因此，我們
認為此一系統可成為新的包含細胞的抗氧化實驗模式。
英文摘要
Previously Daljeet et al, using a 14CO2 quantification method, have demonstrated the generation of hydroxyl radical by arachidonic acid (AA) in platelets. In
experiment, we detected a hydroxyl radical signal induced by AA by electron spin resonance (ESR) techniques in using spin traps such as DMPO
(5,5-dimethyl-1-pyrroline-N-oxide). Three mechanisms have been proposed to the generation of hydroxyl radical by AA: lipoxygenase, cyclooxygenase, and NADPH oxidase. We proposed that blood platelets can produce hydroxyl radical when reacting with AA via 12-lipoxygenase pathway. In addition, we examine the free radical scavenger activity of some natural products such as resvertrol, rutin, quercetin, and lycopene by using this experiment system. Our results showed that AA induced hydroxyl radical formation was inhibited by these antioxidants. Finally, we’ve found g = 2.006 radical generation due to inhibit 12-lipoxygenase activity, leading to produce self-destructive species in accumulation of intermediate I, II at highly concentration of peroxides. In this study, we attempted to directly detect and identify free radicals formed from AA in human platelets and investigate the precise
mechanisms. We suggest that this cell-containing system can be a new antioxidant experimental model.
