Monteith D K, Ding D, Chen Y T, Michalopoulos G, Strom S C
Department of Biological Sciences, Indiana University-Purdue University, Fort Wayne 46805.
Toxicol Appl Pharmacol. 1990 Sep 15;105(3):460-71. doi: 10.1016/0041-008x(90)90149-o.
Exposure of cells to microsomal enzyme inducers can modify the potency of many carcinogens. We have examined the steady-state level of RNA from the P(1)450 gene and the metabolism of benzo[a]pyrene (BP) in primary cultures of human hepatocytes exposed for up to 4 days to 12.5 microM benzanthracene (BA), and in uninduced control cultures. While the steady-state levels of RNA from the P(1)450 gene were nondetectable in uninduced (DMSO only) human hepatocytes, 12.5 microM BA-induced AHH activity, BP metabolism, and/or P(1)450-specific RNA in hepatocytes from seven human cases were investigated. RNA levels specific for the P(1)450 gene appeared maximal at 24 hr following exposure to BA, whereas, the protein, as determined by AHH enzyme activity from BA-induced hepatocytes, continued to increase up to the last time point examined, 72 hr. BA induction for 96 hr increased metabolism of BP (initial concentration of BP, 10 microM) over a time course of 3, 6, 12, and 24 hr of incubation with BP compared with that of controls. The major metabolites of BP produced by human hepatocytes in culture were the unidentified polar BP metabolite(s), possibly polyhydroxylated. BA induction caused approximately a twofold increase in these metabolites. BA-induced cultures showed an increase in glutathione conjugation compared to that in controls. The percentage of glucuronide and sulfate conjugates remains similar in all cultures. Total binding of tritium label BP to DNA was 1.3-fold to fivefold greater in induced cultures, and related more to total metabolism than to production of a specific metabolite. Exposure of human hepatocytes in vitro to BA leads to a large increase in the steady-state level of the RNA specific for the P(1)450 gene and an increase metabolism of BP.
将细胞暴露于微粒体酶诱导剂下可改变许多致癌物的效力。我们检测了暴露于12.5微摩尔苯并蒽（BA）长达4天的原代人肝细胞以及未诱导的对照培养物中，来自P(1)450基因的RNA稳态水平和苯并[a]芘（BP）的代谢情况。虽然在未诱导（仅二甲基亚砜）的人肝细胞中检测不到来自P(1)450基因的RNA稳态水平，但我们研究了12.5微摩尔BA诱导的7例人肝细胞中的芳烃羟化酶（AHH）活性、BP代谢和/或P(1)450特异性RNA。暴露于BA后24小时，P(1)450基因特异性RNA水平似乎达到最大值，而通过BA诱导的肝细胞中的AHH酶活性测定的蛋白质水平，在检测的最后时间点（72小时）之前持续增加。与对照相比，BA诱导96小时可在与BP孵育3、6、12和24小时的时间过程中增加BP（初始浓度为10微摩尔）的代谢。培养的人肝细胞产生的BP主要代谢产物是未鉴定的极性BP代谢物（可能是多羟基化的）。BA诱导使这些代谢物增加了约两倍。与对照相比，BA诱导的培养物中谷胱甘肽结合增加。所有培养物中葡萄糖醛酸和硫酸盐结合物的百分比保持相似。氚标记的BP与DNA的总结合在诱导培养物中高1.3倍至5倍，并且更多地与总代谢相关而非特定代谢物的产生。体外将人肝细胞暴露于BA会导致P(1)450基因特异性RNA的稳态水平大幅增加以及BP代谢增加。
