Luukkanen L, Elovaara E, Lautala P, Taskinen J, Vainio H
Department of Pharmacy, University of Helsinki, Finland.
Pharmacol Toxicol. 1997 Mar;80(3):152-8. doi: 10.1111/j.1600-0773.1997.tb00389.x.
Rats were treated with acetone, pyrazole, phenobarbital, 4,4'-methylenebis-(2-chloroaniline) (MOCA), 3-methylcholanthrene, creosote oil, or a mixture of polychlorinated biphenyls (Aroclor 1254) to study the inducibility and enzyme kinetics of UDP-glucuronosyltransferases towards 1-hydroxypyrene, which is a human metabolite and a urinary biomarker of exposure to pyrene. The rate of 1-hydroxypyrene glucuronidation was analyzed in rat liver microsomes by a fluorometric HPLC assay of the formed glucuronide. The apparent K(m) and Vmax values in untreated controls (K(m) = 0.27 mM; Vmax = 31 nmol/min./mg protein) did not differ markedly from those in rats treated with acetone, pyrazole or phenobarbital, whereas the significantly decreased K(m) and increased Vmax values of the rats treated with the carcinogenic chemicals, MOCA (0.11; 51), creosote (0.06; 137), 3-methylcholanthrene (0.07; 141) or the Aroclor-1254 polychlorinated biphenyl (PCB) mixture (0.08; 226), implicated major changes in the hepatic expression of UDP-glucuronosyltransferases. 1-Hydroxypyrene proved to be a high affinity substrate and a sensitive marker of the polycyclic aromatic hydrocarbon (PAH) metabolizing UDP-glucuronosyltransferase(s). Catalytically, the most efficient isoforms were induced in creosote, 3-methylcholanthrene and PCB-treated rats showing Vmax/K(m) ratios which were 22-27 times greater than in untreated controls. Our findings suggest the existence of a 3-methylcholanthrene type inducible and a functionally efficient low-K(m)/ high-Vmax form(s) of UDP-glucuronosyltransferase(s) that detoxify 1-hydroxypyrene and probably other polycyclic aromatic hydrocarbons as well.
用丙酮、吡唑、苯巴比妥、4,4'-亚甲基双(2-氯苯胺)(MOCA)、3-甲基胆蒽、杂酚油或多氯联苯混合物(Aroclor 1254)处理大鼠，以研究UDP-葡萄糖醛酸基转移酶对1-羟基芘的诱导性和酶动力学，1-羟基芘是一种人体代谢产物，也是接触芘的尿液生物标志物。通过对形成的葡萄糖醛酸化物进行荧光HPLC分析，测定大鼠肝微粒体中1-羟基芘葡萄糖醛酸化的速率。未处理对照组的表观K(m)和Vmax值(K(m)=0.27 mM；Vmax=31 nmol/min./mg蛋白质)与用丙酮、吡唑或苯巴比妥处理的大鼠相比，无明显差异，而用致癌化学物质MOCA(0.11；51)、杂酚油(0.06；137)、3-甲基胆蒽(0.07；141)或Aroclor-1254多氯联苯(PCB)混合物(0.08；226)处理的大鼠，其K(m)显著降低，Vmax升高，这表明UDP-葡萄糖醛酸基转移酶的肝脏表达发生了重大变化。1-羟基芘被证明是多环芳烃(PAH)代谢UDP-葡萄糖醛酸基转移酶的高亲和力底物和敏感标志物。在催化方面，杂酚油、3-甲基胆蒽和PCB处理的大鼠中诱导出最有效的同工型，其Vmax/K(m)比值比未处理对照组高22-27倍。我们的研究结果表明，存在一种3-甲基胆蒽型可诱导的、功能上有效的低K(m)/高Vmax形式的UDP-葡萄糖醛酸基转移酶，可使1-羟基芘以及可能的其他多环芳烃解毒。
