環境強致癌物7-氯苯幷[a]蔥體外代謝和DNA加成物合成實驗能量限制的影響   全文下載

Effect of Caloric Restriction on in Vitro Metabolism and DNA Binding of the Environmental Potent Thmorigen 7-Chlorobenz[a]anthracene

環境污染致癌物-7-氯苯?[a]蔥的代謝和DNA加成物合成實驗中，對所使用的小鼠施予能量限制，取得9個月大的雄性B6C3F1小鼠和9或12個月大的雌性B6C3F1小鼠之肝臟微粒體，研究其對實驗結果所造成的影響。小鼠從出生開始，以正常飲食飼養；14週後逐步能量限制，到16週以餵食正常飲食之60%能量；9個月和12個月大處理之，製備得到微粒體。微粒體和7-氯苯?[a]蔥的體外代謝實驗後，所得代謝物經過萃取、逆相高壓液相層析儀純化後，與標準品比對他們的紫外-可見光譜和質譜圖譜後，證明有10種代謝物，分別如下：反式-3,4-二氫二醇-7-氯苯?[a]蔥；反式-5,6-二氫二醇-7-氯苯?[a]蔥；反式-8,9-二氫二醇-7-苯?[a]蔥；反式-10,11-二氫二醇-7-氯苯?[a]蔥；反式-5,6-環氧-7-氯苯?[a]蔥；和4-, 5-, 6-, 8-, 9-羥基-7-氯苯?[a]蔥。反式-3,4-二氫二醇-7-氯苯?[a]蔥的代謝量，正常飲食之微粒體代謝實驗較能量限制者高；同時，代謝也發生在有公牛胸腺DNA的情況下，結果產生修飾的DNA，藉由32P後標記後，薄膜層析和高壓液相層析儀來分離與分析，所有實驗中只發現一個DNA加成物，即是由反式-3,4-二氫二醇-7-苯?[a]蔥衍生的加成物。相同性別和年齡的小鼠中，微粒體合成DNA加成物的量，能量限制的較正常飲食者低；因此，我們的結果顯示能量限制抑制即將發生之代謝物-反式-3,4-二氫二醇-7-氯苯?[a]蔥的形成和明顯地降低其DNA加成物的形成。"

The effect of caloric restriction (CR) on the metabolism and DNA binding of 7-chlorobenz[a]anthracene (7-Cl-BA), a tumorigenic environmental contaminant, by liver microsomes of 9-month-old male B6C3F1 mice and 9- and 12-month-old female B6C3F1 mice was studied. Mice were fed ad libitum (AL), or starting at 14 weeks of age, received 60% of the calories consumed by control mice and were sacrified at 9 or 12 months of age. After microsomal incubations, metabolites were extracted, purified by reversed-phase HPLC, and identified by comparison of their UV-visible and mass spectral data with those of standards. In each case, ten metabolites were identified: 7-Cl-BA trans-3,4-dihydrodiol, 7-Cl-BA trans-5,6-dihydrodiol, 7-Cl-BA trans-8,9-dihydrodiol, 7-Cl-BA trans-10,11-dihydrodiol, 7-Cl-BA 5,6-epoxide, and 4-, 5-, 6-, 8-, and 9-0H-7-ClBA. The quantity of 7-Cl-BA trans-3,4-dihydrodiol was formed in a higher yield from the AL microsomes than from the CR microsomes. Metabolism was also performed in the presence of calf thymus DNA, and the resulting modified DNA was isolated and analyzed by both 32P-postlabeling/TLC and 32P-postlabeling/HPLC. Only one DNA adduct, which was derived from 7-Cl-BA trans-3,4-dihydrodiol, was detected in all cases. The levels of adduct formation from CR microsomes were lower than those from the AL microsomes of the same sex and same age. Thus, our results indicate that CR inhibits the formation of the proximate metabolite, 7-Cl-BA trans-3,4- dihydrodiol, and significantly reduces the DNA adduct formation. 環境污染致癌物-7-氯苯幷[a]蔥的代謝和DNA加成物合成實驗中，對所使用的小鼠施予能量限制，取得9個月大的雄性B6C3F1小鼠和9或12個月大的雌性B6C3F1小鼠之肝臟微粒體，研究其對實驗結果所造成的影響。小鼠從出生開始，以正常飲食飼養；14週後逐步能量限制，到16週以餵食正常飲食之60%能量；9個月和12個月大處理之，製備得到微粒體。微粒體和7-氯苯幷[a]蔥的體外代謝實驗後，所得代謝物經過萃取、逆相高壓液相層析儀純化後，與標準品比對他們的紫外-可見光譜和質譜圖譜後，證明有10種代謝物，分別如下：反式-3,4-二氫二醇-7-氯苯幷[a]蔥；反式-5,6-二氫二醇-7-氯苯幷[a]蔥；反式-8,9-二氫二醇-7-苯幷[a]蔥；反式-10,11-二氫二醇-7-氯苯幷[a]蔥；反式-5,6-環氧-7-氯苯幷[a]蔥；和4-, 5-, 6-, 8-, 9-羥基-7-氯苯幷[a]蔥。反式-3,4-二氫二醇-7-氯苯幷[a]蔥的代謝量，正常飲食之微粒體代謝實驗較能量限制者高；同時，代謝也發生在有公牛胸腺DNA的情況下，結果產生修飾的DNA，藉由32P後標記後，薄膜層析和高壓液相層析儀來分離與分析，所有實驗中只發現一個DNA加成物，即是由反式-3,4-二氫二醇-7-苯幷[a]蔥衍生的加成物。相同性別和年齡的小鼠中，微粒體合成DNA加成物的量，能量限制的較正常飲食者低；因此，我們的結果顯示能量限制抑制即將發生之代謝物-反式-3,4-二氫二醇-7-氯苯幷[a]蔥的形成和明顯地降低其DNA加成物的形成。