Connors M S, Malfatti M A, Felton J S
Department of Biological Sciences, San Jose State University, CA 95192-0100, USA.
Chem Biol Interact. 1995 May 19;96(2):185-202. doi: 10.1016/0009-2797(94)03595-y.
Precision-cut liver slices prepared from Aroclor 1254 pretreated male rats were used to investigate the metabolism of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). The acetyltransferase and sulfotransferase inhibitors, pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP), and the cytochrome P450 inhibitor, alpha-naphthoflavone (ANF), were used to modulate PhIP metabolism and DNA and protein adduct formation. PCP and DCNP had similar effects on the formation of some PhIP metabolites. PCP and DCNP decreased the formation of 4'-(2-amino-1-methylimidazo[4,5-b]pyrid-6-yl)phenyl sulfate (4'-PhIP-sulfate) and 2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP)-glucuronide to 10% and 55% of controls, respectively. 2-Amino-1-methyl-4'-hydroxy-6-phenylimidazo[4,5-b]pyridine (4'-hydroxy-PhIP) was increased by 50% relative to control levels due to PCP and DCNP treatment. PCP and DCNP had different effects on the formation of other PhIP metabolites. Metabolite formation as percent of control for the uncharacterized metabolite, 'Peak A', was 50% and 100% in incubations with PCP and DCNP, respectively. Formation of 4'-hydroxy-PhIP-glucuronide was decreased to 10% of controls with PCP and increased to 147% of controls with DCNP. PCP and DCNP had no effect on the formation of an unidentified metabolite, 'Peak B'. ANF decreased metabolite formation by 60-95%. None of the enzyme inhibitors had a statistically significant effect on PhIP-DNA binding. Covalent binding of PhIP to protein was slightly decreased in incubations containing DCNP or PCP. The lack of significant changes in covalent binding to either DNA or protein suggests that additional pathways may be important in PhIP bioactivation in rat liver slices. With ANF, there was a significant decrease (35%) in protein binding. These observations on the effects of PCP, DCNP and ANF on PhIP metabolism as well as on covalent binding of PhIP to tissue macromolecules are in close agreement with what was reported earlier in hepatocytes. This indicates that tissue slices from various target tissues for tumorigenesis will be a useful in vitro tool for future studies on heterocyclic amine metabolism. This study provides another important example of the utility of precision-cut tissue slices to investigate xenobiotic metabolism and toxicity.
从经艾氏剂1254预处理的雄性大鼠制备的精密肝切片用于研究2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶（PhIP）的代谢。使用乙酰转移酶和磺基转移酶抑制剂五氯苯酚（PCP）和2,6-二氯-4-硝基苯酚（DCNP）以及细胞色素P450抑制剂α-萘黄酮（ANF）来调节PhIP代谢以及DNA和蛋白质加合物的形成。PCP和DCNP对某些PhIP代谢物的形成有相似的影响。PCP和DCNP分别将4'-（2-氨基-1-甲基咪唑并[4,5-b]吡啶-6-基）苯基硫酸盐（4'-PhIP-硫酸盐）和2-（羟基氨基）-1-甲基-6-苯基咪唑并[4,5-b]吡啶（N-羟基-PhIP）-葡糖醛酸酯的形成降低至对照的10%和55%。由于PCP和DCNP处理，2-氨基-1-甲基-4'-羟基-6-苯基咪唑并[4,5-b]吡啶（4'-羟基-PhIP）相对于对照水平增加了50%。PCP和DCNP对其他PhIP代谢物的形成有不同的影响。在与PCP和DCNP孵育时，未鉴定代谢物“峰A”作为对照百分比的代谢物形成分别为50%和100%。4'-羟基-PhIP-葡糖醛酸酯的形成在PCP处理下降低至对照的10%，在DCNP处理下增加至对照的147%。PCP和DCNP对未鉴定代谢物“峰B”的形成没有影响。ANF使代谢物形成降低60 - 95%。没有一种酶抑制剂对PhIP-DNA结合有统计学上显著的影响。在含有DCNP或PCP的孵育中，PhIP与蛋白质的共价结合略有降低。与DNA或蛋白质共价结合缺乏显著变化表明，其他途径可能在大鼠肝切片中PhIP的生物活化中起重要作用。使用ANF时，蛋白质结合有显著降低（35%）。关于PCP、DCNP和ANF对PhIP代谢以及PhIP与组织大分子共价结合的影响的这些观察结果与早期在肝细胞中报道的结果密切一致。这表明来自各种肿瘤发生靶组织的组织切片将是未来杂环胺代谢研究的有用体外工具。本研究提供了另一个重要例子，说明精密组织切片在研究外源化合物代谢和毒性方面的实用性。
