The enzymatic formation and chemical reactivity of quinone methides correlate with alkylphenol-induced toxicity in rat hepatocytes.
The enzymatic formation and chemical reactivity of quinone methides correlate with alkylphenol-induced toxicity in rat hepatocytes.
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DOI：
10.1021/tx00030a014
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发表时间：
1992-11
影响因子：
4.1
通讯作者：
J. Bolton;L. Valerio;John A. Thompson
中科院分区：
文献类型：
--
作者：
J. Bolton;L. Valerio;John A. Thompson
研究了邻烷基取代基对细胞色素p450催化苯酚氧化生成对醌类化合物（QM's； 4-亚甲基-2,5-环己二烯-1-酮）的影响，以及对QM's的4-亚甲基碳亲核加成速率的影响。所研究的4-甲基苯酚衍生物有BHT（2,6-二叔丁基）、BHTOH[6-叔丁基-2-（羟基-叔丁基）]、BDMP（2-叔丁基-6-甲基）、BMP（2-叔丁基）、TMP（2,6-二甲基）和DMP（2-甲基）。P450的QM形成估计在0.17-0.70 nmol/(nmol)之间。Min), 16-62 pmol/(10(6)个细胞。Min)在分离的大鼠肝细胞中。合成由BHT （BHT-QM）、BHTOH （BHTOH-QM）、BDMP （BDMP-QM）和TMP （TMP-QM）衍生的QM，并测定其与水和还原性谷胱甘肽（GSH）的反应速率。BDMP-QM和TMP-QM反应性最强，BHT-QM消耗相对较慢，BHTOH-QM表现为中间反应性。这些速率的变化是由氢键与羰基氧的差异来解释的，这影响了亲核攻击部位的正电荷密度。在BMP、BDMP和BHTOH的培养过程中，肝细胞活力的丧失发生在GSH耗尽之前。马来酸二乙酯预处理肝细胞可加重烷基酚毒性，而美替拉酮对肝细胞有保护作用。这些数据，以及关于QM's形成和反应性的信息，有力地支持了QM's介导烷基化4-甲基苯酚在大鼠肝细胞中的毒性的提议。
The effects of o-alkyl substituents on both the cytochrome P450-catalyzed oxidation of phenols to p-quinone methides (QM's; 4-methylene-2,5-cyclohexadien-1-ones), and on the rates of nucleophilic additions to the 4-methylene carbon of QM's were investigated. The derivatives of 4-methylphenol studied were BHT (2,6-di-tert-butyl), BHTOH [6-tert-butyl-2-(hydroxy-tert-butyl)], BDMP (2-tert-butyl-6-methyl), BMP (2-tert-butyl), TMP (2,6-dimethyl), and DMP (2-methyl). QM formation was estimated to be in the range 0.17-0.70 nmol/(nmol of P450.min) in rat liver microsomes and 16-62 pmol/(10(6) cells.min) in isolated rat hepatocytes. QM's derived from BHT (BHT-QM), BHTOH (BHTOH-QM), BDMP (BDMP-QM), and TMP (TMP-QM) were synthesized and their rates of reaction with water and reduced glutathione (GSH) determined. BDMP-QM and TMP-QM were the most reactive, BHT-QM was consumed relatively slowly, and BHTOH-QM displayed intermediate reactivity. These variations in rate were rationalized by differences in hydrogen bonding with the carbonyl oxygen, which affects positive charge density at the site of nucleophilic attack. The loss of hepatocyte viability during incubations with BMP, BDMP, and BHTOH was preceded by GSH depletion. Pretreatment of hepatocytes with diethyl maleate exacerbated alkylphenol toxicity, and metyrapone protected the cells. These data, together with information on the formation and reactivity of QM's, strongly support the proposal that QM's mediate the toxicity of alkylated 4-methylphenols in rat hepatocytes.