Keller D A, Carpenter S C, Cagen S Z, Reitman F A
E.I. du Pont de Nemours and Company, Haskell Laboratory for Toxicology and Industrial Medicine, Newark, Delaware 19714, USA.
Toxicol Appl Pharmacol. 1997 May;144(1):36-44. doi: 10.1006/taap.1996.8098.
4-Vinylcyclohexene (4-VCH), the dimer of 1,3-butadiene, is an ovarian toxicant in mice due to the formation of a diepoxide metabolite, but the tissue-specific site of formation of the metabolites is unknown. Microsomal preparations from liver, lung, and ovaries obtained from female Crl:CD BR rats and female B6C3F1 mice were tested for their ability to metabolize the following reactions: 4-VCH to 4-VCH-1,2-epoxide and 4-VCH-7,8-epoxide; 4-VCH-1,2-epoxide to 4-VCH diepoxide and 4-VCH-1,2-diol; 4-VCH-7,8-epoxide to 4-VCH diepoxide and 4-VCH-7,8-diol; and hydrolysis of 4-VCH diepoxide. Microsomes were incubated with the test chemical and the reaction products were analyzed by gas chromatography. Rat liver and lung microsomes and mouse liver and lung microsomes metabolized 4-VCH to 4-VCH-1,2-epoxide at detectable rates. Mouse liver had a Vmax for the reaction that was 56-fold higher than that for rat liver (11.1 and 0.20 nmol/min/mg protein, respectively). The Vmax for mouse lung was 2-fold higher than that for rat lung. 4-VCH-1,2-epoxide formation was not detected in ovarian microsomes from rats or mice. Metabolism of 4-VCH to 4-VCH-7,8-epoxide was detected in microsomes from rat liver and mouse liver and lung, at rates very low compared to those for metabolism to the 1,2-epoxide. Rat and mouse liver had very similar K(m) and Vmax values for metabolism of 4-VCH-1,2-epoxide to 4-VCH diepoxide. The Vmax for rat liver was 3.69 and for mouse liver was 5.35 nmol/min/mg protein. Rat and mouse ovaries did not have detectable capacity to metabolize 4-VCH-1,2-epoxide to the diepoxide. Rat and mouse liver and lung have very similar K(m) and Vmax values for metabolism of 4-VCH-7,8-epoxide to the diepoxide, while ovaries did not have detectable rates for this reaction. Hydrolysis of 4-VCH-1,2-epoxide to 4-VCH-1,2-diol was at similar rates in rat and mouse liver microsomes. Hydrolysis of 4-VCH-7,8-epoxide to 4-VCH-7,8-diol was detected only in rat liver microsomes. Hydrolysis of 4-VCH diepoxide was detected in rat and mouse liver and lung, and in rat ovary microsomes. The Vmax for rat liver was 9-fold greater than that for mouse liver (5.51 and 0.63 nmol/min/mg protein, respectively), and lung and ovary tissues were not as active as rat liver. The balance of activation versus detoxication reactions in rats and mice suggests that the mouse may be more susceptible to 4-VCH toxicity because of generation of high levels of epoxide metabolites. In general, the mouse is more efficient at metabolism of 4-VCH to epoxides than is the rat. In contrast, the rat may be more efficient at hydrolysis of epoxides. Thus, the rat would tend to produce a lower concentration of epoxide metabolites than the mouse, at equal doses of 4-VCH.
1,3 - 丁二烯的二聚体4 - 乙烯基环己烯（4 - VCH）是小鼠卵巢的一种毒物，因其会形成一种双环氧化物代谢物，但代谢物形成的组织特异性位点尚不清楚。对从雌性Crl:CD BR大鼠和雌性B6C3F1小鼠获取的肝脏、肺和卵巢的微粒体制剂进行测试，以检测它们代谢以下反应的能力：4 - VCH转化为4 - VCH - 1,2 - 环氧化物和4 - VCH - 7,8 - 环氧化物；4 - VCH - 1,2 - 环氧化物转化为4 - VCH双环氧化物和4 - VCH - 1,2 - 二醇；4 - VCH - 7,8 - 环氧化物转化为4 - VCH双环氧化物和4 - VCH - 7,8 - 二醇；以及4 - VCH双环氧化物的水解。将微粒体与测试化学品一起孵育，并通过气相色谱法分析反应产物。大鼠肝脏和肺微粒体以及小鼠肝脏和肺微粒体以可检测到的速率将4 - VCH代谢为4 - VCH - 1,2 - 环氧化物。小鼠肝脏该反应的Vmax比大鼠肝脏高56倍（分别为11.1和0.20 nmol/分钟/毫克蛋白）。小鼠肺的Vmax比大鼠肺高2倍。在大鼠或小鼠的卵巢微粒体中未检测到4 - VCH - 1,2 - 环氧化物的形成。在大鼠肝脏、小鼠肝脏和肺的微粒体中检测到4 - VCH代谢为4 - VCH - 7,8 - 环氧化物，但与代谢为1,2 - 环氧化物的速率相比非常低。大鼠和小鼠肝脏将4 - VCH - 1,2 - 环氧化物代谢为4 - VCH双环氧化物的K(m)和Vmax值非常相似。大鼠肝脏的Vmax为3.69，小鼠肝脏的Vmax为5.35 nmol/分钟/毫克蛋白。大鼠和小鼠卵巢没有可检测到的将4 - VCH - 1,2 - 环氧化物代谢为双环氧化物的能力。大鼠和小鼠肝脏及肺将4 - VCH - 7,8 - 环氧化物代谢为双环氧化物的K(m)和Vmax值非常相似，而卵巢中该反应的速率未检测到。4 - VCH - 1,2 - 环氧化物水解为4 - VCH - 1,2 - 二醇在大鼠和小鼠肝脏微粒体中的速率相似。4 - VCH - 7,8 - 环氧化物水解为4 - VCH - 7,8 - 二醇仅在大鼠肝脏微粒体中检测到。4 - VCH双环氧化物的水解在大鼠和小鼠肝脏、肺以及大鼠卵巢微粒体中均检测到。大鼠肝脏的Vmax比小鼠肝脏大9倍（分别为5.51和0.63 nmol/分钟/毫克蛋白），肺和卵巢组织的活性不如大鼠肝脏。大鼠和小鼠中活化与解毒反应的平衡表明，由于产生高水平的环氧化物代谢物，小鼠可能对4 - VCH毒性更敏感。一般来说，小鼠将4 - VCH代谢为环氧化物的效率比大鼠更高。相比之下，大鼠可能在环氧化物水解方面更有效。因此，在相同剂量的4 - VCH下，大鼠产生的环氧化物代谢物浓度往往比小鼠低。
