Miranda C L, Henderson M C, Williams D E, Buhler D R
Department of Agricultural Chemistry, Oregon State University, Corvallis 97331, USA.
Toxicol Appl Pharmacol. 1997 Jan;142(1):123-32. doi: 10.1006/taap.1996.8021.
Liver microsomes from juvenile trout metabolized DMBA to unknown highly polar metabolites (X) and to DMBA-t-5,6-diol, DMBA-t-8,9-diol, 7-OHM-12-MBA, 7M-12-OHMBA, 2-OH-DMBA, 4-OH-DMBA, and trace amounts of DMBA-t-3,4-diol. Treatment of trout with beta-naphthoflavone (BNF) and isosafrole (ISF) increased the formation of these products except for the hydroxymethyl derivatives of DMBA. The production of DMBA-t-3,4-diol, 2-OH-DMBA, and 4-OH-DMBA was much greater in BNF-induced liver microsomes than that in ISF-induced liver microsomes. In contrast, the yield of DMBA-t-8,9-diol and 7-OHM-12-MBA was greater in ISF-induced microsomes than that in BNF-induced microsomes. Trout CYP1A1 (P450 LM4b) purified from BNF-treated trout catalyzed the formation of the same metabolites generated by BNF-induced microsomes in the presence of added human microsomal EH. The constitutive forms of P450 isolated from untreated trout such as P450s LMC3, LMC4, and LMC5, CYP2M1 (P450 LMC1), and CYP2K1 (P450 LMC2) did not produce any of the DMBA metabolites (except for DMBA-t-8,9-diol by CYP2K1) generated by the trout microsomes. Generation of DMBA-DNA and DMBA-protein adducts in vitro was enhanced by treatment of trout with BNF and by ISF to a lesser extent. Formation of adducts and DMBA diols by BNF-induced liver microsomes and by trout CYP1A1 was completely blocked by the CYP1A inhibitor ellipticine (100 microM). These results suggest that the BNF-inducible trout P450 (CYP1A), not the constitutive P450s, is the major catalyst for the biotransformation of DMBA to metabolites that bind to macromolecules.
幼年鳟鱼的肝脏微粒体将二甲基苯并蒽（DMBA）代谢为未知的高极性代谢物（X）以及DMBA - t - 5,6 - 二醇、DMBA - t - 8,9 - 二醇、7 - OHM - 12 - MBA、7M - 12 - OHMBA、2 - OH - DMBA、4 - OH - DMBA和痕量的DMBA - t - 3,4 - 二醇。用β - 萘黄酮（BNF）和异黄樟素（ISF）处理鳟鱼增加了这些产物的形成，但DMBA的羟甲基衍生物除外。在BNF诱导的肝脏微粒体中，DMBA - t - 3,4 - 二醇、2 - OH - DMBA和4 - OH - DMBA的生成量比ISF诱导的肝脏微粒体中的生成量要多得多。相比之下，在ISF诱导的微粒体中，DMBA - t - 8,9 - 二醇和7 - OHM - 12 - MBA的产量比BNF诱导的微粒体中的产量要高。从经BNF处理的鳟鱼中纯化得到的鳟鱼细胞色素P450 1A1（P450 LM4b）在添加人微粒体环氧化物水解酶（EH）的情况下，催化生成了与BNF诱导的微粒体所产生的相同代谢物。从未经处理的鳟鱼中分离得到的细胞色素P450的组成型形式，如P450s LMC3、LMC4和LMC5、细胞色素P450 2M1（P450 LMC1）和细胞色素P450 2K1（P450 LMC2），不会产生鳟鱼微粒体所生成的任何DMBA代谢物（细胞色素P450 2K1产生DMBA - t - 8,9 - 二醇除外）。用BNF处理鳟鱼以及用ISF处理（程度较轻）可增强体外DMBA - DNA和DMBA - 蛋白质加合物的生成。BNF诱导的肝脏微粒体和鳟鱼细胞色素P450 1A1所形成的加合物和DMBA二醇可被细胞色素P450 1A抑制剂玫瑰树碱（100 microM）完全阻断。这些结果表明，BNF可诱导的鳟鱼细胞色素P450（CYP1A）而非组成型细胞色素P450是将DMBA生物转化为与大分子结合的代谢物的主要催化剂。
