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題 名 | 維生素A 中毒及肝微粒體酵素系統於維生素A 代謝上所扮演之角色 |
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作 者 | 劉珍芳; 黃青真; | 書刊名 | 中華民國營養學會雜誌 |
卷 期 | 16:1/2 民80.04 |
頁 次 | 頁139-155 |
分類號 | 411.38 |
關鍵詞 | 代謝; 肝微粒體; 維生素A中毒; 酵素; |
語 文 | 中文(Chinese) |
中文摘要 | 維生素A對於哺乳動物而言是非常重要的營養素,在維持正常視覺、黏膜細胞之完整性、細胞之分化、生長及發育上均扮演重要的角色。近年來,常用高劑量的維生素A來治療乾眼症、生殖能力不全症、各種皮膚疾等。但服用高劑量之維生素A會造成肝中毒,此外,老鼠於懷孕期間服用過量之維生素A時,會造成型態上或行為上的畸型。於人類的案例報告中亦發現,母親於懷孕時服用高劑量的維生素A時,會造成先天性的功能不全或畸型。近年來之研究發現,兩種維生素A之化合物─視網醇 ( retinol)及視網酸(retinoic acid),可經動物肝微粒體中之藥物代謝酵素系統cytochrome P-450 system代謝,且生成較具極性之代謝物4-hydroxy-retinol, 4-hydroxy-retinoic acid, 4-oxo-retinoic acid等。其中以稱為P450 II C8(於人類)或P450 II C7(於老鼠)之同功酉每具有最高之代謝活性。一般情形下,此同功酉每於肝微粒體中之活性低,但可經由維生素A、酒精或其他藥物之誘發後增加。所以,可以進一步地證實,cytochrome P-450酵素系統不僅在藥物、環境毒物之代謝上具有重要性,於一般生理代謝途徑(例如維生素A代謝)上可能亦扮演著重要的角色。 |
英文摘要 | Adequate intake of vitamin A is essential for the maintenance ofnormal vision, integriety of epithelial structure, cellular differentiation, growth, and development. Large doses of vitamin A is usedtherapeutically for a variety of dermatologic diseases, hypogonadism, abnormal dark adapatlon, xerophthalmia etc. However, it is noteworthy that excess intake of vitamin A 1s hepatotoxic. Moreever, hypervltaminosis A has been shown to be teratogenic in animal study and to berelated to congenital malformation in newborn of mother overdosed by vitamin A during pregnancy. Recently, it has been demonstrated that the two major vitamin Acompounds-retinol and retinoic acid, could be oxidized to more polarmetabolites, including: 4-hydroxy-retinol, 4-hydroxy-retinoic acid and4-oxo-retino1c acid by the liver microsomat cytochrome P-450containing monooxygenase. One of the cytochrome P-450 isozymes-P450IIC8 (in human) or P450IIC7 (also called P450f, in rat) showed thehighest metabolizing activity. The activity of this constitutive P450 is ozyme in the liver microsome of human and rat is low but could beindued to higher level by certain substances, such as ethanol, vitaminA and drugs. Therefore, the microsomal P450s not only play a major role in thedetoxificatlon of foreigh compounds but also 1s involved in normalphysiological processes, including vitamin A metabolism. It mayparticipate in maintaining the balance between those vitamin Aconcentration that promote cellular integrity (and oppose thedevelopment of cancer) and those concentatlon that cause cellulartoxicity, further studies are necessary to clearify this role. |
本系統中英文摘要資訊取自各篇刊載內容。