Johnsen N M, Nyholm S H, Haug K, Scholz T, Holme J A
Department of Environmental Medicine, National Institute of Public Health, Oslo, Norway.
Chem Biol Interact. 1998 Jun 5;113(3):217-37. doi: 10.1016/s0009-2797(98)00037-4.
The metabolism of radiolabelled benz(j)aceanthrylene (B(j)A) was studied by high performance liquid chromatography (HPLC) using suspensions of hepatocytes and liver microsomes from control- or Aroclor 1254 (PCB)-treated rats, or with human liver microsomes (five different donors) as activation systems. The major metabolites formed in hepatocytes were sulfate conjugates, indicating that sulfation is an important detoxication pathway for B(j)A. In incubations with B(j)A and rat or human liver microsomes, the major metabolite formed was B(j)A-1,2-diol. Studies with rat liver microsomes using antibodies (Ab) towards either P4501A1, 1A2 or 3A2, resulted in approximately 30% reduction in covalent binding with all Ab-using microsomes from control animals, whereas with microsomes from PCB-treated animals an 85% reduction was observed using Ab towards P4501A2, and only minor reductions were observed with 1A1 or 3A2. When compared to B(j)A and benzo(a)pyrene (B(a)P), benz(1)aceanthrylene (B(l)A) caused higher numbers of revertants in the Salmonella assay when plated with rat liver microsomes from control animals or human liver microsomes. The total DNA adduct levels in hepatocytes from control animals after 2 h exposure to 30 micrograms/ml (120 microM) B(j)A or B(l)A, as measured by the 32P-postlabelling technique, were 3.8 +/- 1.5 and 10.1 +/- 5.8 fmol/microgram DNA, respectively. PCB-treatment decreased the total level of B(j)A adducts slightly (1.8 +/- 0.5 fmol/microgram DNA), whereas in contrast the level of B(1)A adducts was increased (24.5 +/- 20.1 fmol/microgram DNA). The major DNA adduct formed in control hepatocytes exposed to B(j)A co-chromatographed with B(j)A-1,2-oxide, which also appeared to be the major adduct formed when rat or human liver microsomes were co-incubated with calf thymus DNA. The total DNA adduct levels in the modified calf thymus DNA after 30 min exposure to 30 micrograms/ml B(j)A, B(l)A or B(a)P using rat liver microsomes form control animals, were 3.6, 66.3 and 1.4 fmol/microgram DNA, respectively. These levels increased to 22.7, 93.3 and 7.4 fmol/microgram DNA, respectively, using microsomes from PCB-treated animals. With human liver microsomes, the total DNA adduct levels after exposure to B(j)A, B(l)A or B(a)P, ranged between 0.4-1.0, 0.3-4.3, and 0.1-0.3 fmol/microgram DNA, respectively. Overall, the present data supports the notion that oxidation at the cyclopenta-ring is an important activation pathway for B(j)A, and indicate that the activation mechanism for B(j)A is similar in rat and human liver tissue.
使用来自对照或经多氯联苯（PCB）-1254处理的大鼠的肝细胞和肝微粒体悬浮液，或用人肝微粒体（五个不同供体）作为活化系统，通过高效液相色谱（HPLC）研究了放射性标记的苯并(j)屈（B(j)A）的代谢。在肝细胞中形成的主要代谢产物是硫酸酯结合物，表明硫酸化是B(j)A的重要解毒途径。在用B(j)A与大鼠或人肝微粒体孵育时，形成的主要代谢产物是B(j)A-1,2-二醇。使用针对P4501A1、1A2或3A2的抗体（Ab）对大鼠肝微粒体进行研究，结果显示与来自对照动物的所有使用抗体的微粒体共价结合减少了约30%，而对于来自PCB处理动物的微粒体，使用针对P4501A2的抗体观察到共价结合减少了85%，而使用针对1A1或3A2的抗体仅观察到轻微减少。与B(j)A和苯并(a)芘（B(a)P）相比，苯并(1)屈（B(l)A）在用来自对照动物的大鼠肝微粒体或人肝微粒体铺板时，在沙门氏菌试验中引起更多的回复突变体。通过32P后标记技术测量，对照动物的肝细胞在暴露于30微克/毫升（120微摩尔）B(j)A或B(l)A 2小时后的总DNA加合物水平分别为3.8±1.5和10.1±5.8飞摩尔/微克DNA。PCB处理使B(j)A加合物的总水平略有降低（1.8±0.5飞摩尔/微克DNA），而相比之下，B(1)A加合物的水平升高（24.5±20.1飞摩尔/微克DNA）。在暴露于B(j)A的对照肝细胞中形成的主要DNA加合物与B(j)A-1,2-氧化物共色谱，当大鼠或人肝微粒体与小牛胸腺DNA共同孵育时，这似乎也是形成的主要加合物。使用来自对照动物的大鼠肝微粒体，小牛胸腺DNA在暴露于30微克/毫升B(j)A、B(l)A或B(a)P 30分钟后的总DNA加合物水平分别为3.6、66.3和1.4飞摩尔/微克DNA。使用来自PCB处理动物的微粒体时，这些水平分别增加到22.7、93.3和7.4飞摩尔/微克DNA。对于人肝微粒体，暴露于B(j)A、B(l)A或B(a)P后的总DNA加合物水平分别在0.4 - 1.0、0.3 - 4.3和0.1 - 0.3飞摩尔/微克DNA之间。总体而言，目前的数据支持环戊环上的氧化是B(j)A的重要活化途径这一观点，并表明B(j)A在大鼠和人肝组织中的活化机制相似。
