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 DMP O (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 ， N ADPH 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-lipoxygenas e 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。
花生四烯酸對人類血小板所產生氫氧自由基之探 討
Previously Daljeet et al, using a 14CO2 quantification method, have demons trated the generation of hydroxyl radical by arachidonic acid (AA) in platelets . In experiment, we detected a hydroxyl radical signal induced by AA by elect ron spin resonance (ESR) techniques in using spin traps such as DMPO (5,5-d imethyl-1-pyrroline-N-oxide). Three mechanisms have been proposed to the g eneration of hydroxyl radical by AA: lipoxygenase, cyclooxygenase, and NA DPH oxidase. We proposed that blood platelets can produce hydroxyl radical when reacting with AA via 12-lipoxygenase pathway. In addition, we examin e the free radical scavenger activity of some natural products such as resvertr ol, rutin, quercetin, and lycopene by using this experiment system. Our results showed that AA induced hydroxyl radical formation was inhibited by these an tioxidants. Finally, we’ve found g = 2.006 radical generation due to inhibit 1 2-lipoxygenase activity, leading to produce self-destructive species in accumu lation 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.
Mechanisms Involved in Arachidonic Acid-
Induced Hydroxyl Radical Formation in Human Platelets.
