Wroblewski V J, Gessner T, Olson J R
Department of Pharmacology and Therapeutics, State University of New York, Buffalo 14214.
Biochem Pharmacol. 1988 Apr 15;37(8):1509-17. doi: 10.1016/0006-2952(88)90012-3.
The present study compared the induction and inhibition of the metabolism of the prototype polycyclic aromatic hydrocarbon, benzo[a]pyrene (BaP), in rat and hamster liver microsomes. The production of total polar metabolites was quantitated by separating 3H-metabolites from [3H]-BaP using reverse-phase thin-layer chromatography. The rate of hepatic microsomal BaP metabolism was similar in the rat and hamster (0.81 vs 0.72 nmol/min/nmol cytochrome P-450 respectively). In the rat, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 5 micrograms/kg, i.p.) and 3-methylcholanthrene (3-MC; 50 mg/kg, i.p., X 3 days) pretreatments doubled the rate of BaP metabolism, whereas phenobarbital pretreatment (PB; 80 mg/kg, i.p., X 3 days) had no effect. In contrast, hamster hepatic microsomal BaP metabolism was elevated 2.3-fold by PB pretreatment, whereas TCDD and 3-MC pretreatments had no effect. Isosafrole pretreatment (ISO; 150 mg/kg, i.p., X 3 days) elevated the rate by almost 2-fold in each species. Another cytochrome P-448-mediated activity, 7-ethoxyresorufin O-deethylase (EROD), was induced by the same compounds that induced BaP metabolism in the rat. In hamster liver microsomes, in contrast to BaP metabolism, EROD was induced by TCDD and 3-MC but not PB or ISO pretreatments. The results suggest differences in the substrate specificity of the cytochromes P-448-450 induced by TCDD, 3-MC and PB in these species. This was supported by the different selectivity of the in vitro inhibitors, metyrapone and 7,8-benzoflavone, towards BaP metabolism and EROD in hepatic microsomes from TCDD- or PB-pretreated rats and hamsters. Reverse-phase HPLC analysis indicated that, while 3-hydroxy-BaP was the major metabolite formed by the untreated rat, untreated hamster liver microsomes formed predominantly BaP-4,5-diol. Microsomes from TCDD-treated rats generated elevated levels of all BaP-diols, diones and 3-hydroxy-BaP, with the major metabolites being BaP-9,10- and BaP-7,8-diols. In contrast, the metabolite profile from TCDD-pretreated hamsters was unchanged from the control. PB-treated hamster microsomes produced elevated levels of BaP-diones and 3-hydroxy-BaP. However, the major hepatic metabolite formed by PB-pretreated hamsters was BaP-4,5-diol, while BaP-9,10- and BaP-7,8-diols were not detected. The results of the study indicate differences in the induced cytochrome P-450s and the generation of toxic BaP metabolites in the liver of the rat and hamster.
本研究比较了原型多环芳烃苯并[a]芘（BaP）在大鼠和仓鼠肝微粒体中的代谢诱导和抑制情况。使用反相薄层色谱法从[³H]-BaP中分离³H-代谢物，对总极性代谢物的生成进行定量。大鼠和仓鼠肝微粒体中BaP的代谢速率相似（分别为0.81和0.72 nmol/分钟/ nmol细胞色素P-450）。在大鼠中，2,3,7,8-四氯二苯并对二噁英（TCDD；5微克/千克，腹腔注射）和3-甲基胆蒽（3-MC；50毫克/千克，腹腔注射，共3天）预处理使BaP代谢速率加倍，而苯巴比妥预处理（PB；80毫克/千克，腹腔注射，共3天）则无影响。相反，PB预处理使仓鼠肝微粒体中BaP代谢升高了2.3倍，而TCDD和3-MC预处理则无影响。异黄樟素预处理（ISO；150毫克/千克，腹腔注射，共3天）使每个物种的代谢速率提高了近2倍。另一种细胞色素P-448介导的活性，7-乙氧基异吩噁唑酮O-脱乙基酶（EROD），在大鼠中由诱导BaP代谢的相同化合物诱导。相比之下，在仓鼠肝微粒体中，与BaP代谢不同，EROD由TCDD和3-MC诱导，但不受PB或ISO预处理的影响。结果表明，TCDD、3-MC和PB在这些物种中诱导的细胞色素P-448-450的底物特异性存在差异。TCDD或PB预处理的大鼠和仓鼠肝微粒体中，体外抑制剂美替拉酮和7,8-苯并黄酮对BaP代谢和EROD的不同选择性支持了这一点。反相高效液相色谱分析表明，未处理的大鼠形成的主要代谢物是3-羟基-BaP，而未处理的仓鼠肝微粒体主要形成BaP-4,5-二醇。TCDD处理的大鼠微粒体中所有BaP-二醇、二酮和3-羟基-BaP的水平都升高，主要代谢物是BaP-9,10-二醇和BaP-7,8-二醇。相比之下，TCDD预处理的仓鼠的代谢物谱与对照相比没有变化。PB处理的仓鼠微粒体中BaP-二酮和3-羟基-BaP的水平升高。然而，PB预处理的仓鼠形成的主要肝代谢物是BaP-4,5-二醇，未检测到BaP-9,10-二醇和BaP-7,8-二醇。研究结果表明，大鼠和仓鼠肝脏中诱导的细胞色素P-450以及有毒BaP代谢物的生成存在差异。
