Fisher R, Brendel K, Hanzlik R P
Department of Pharmacology, University of Arizona, Tucson 85724.
Chem Biol Interact. 1993 Sep;88(2-3):191-8. doi: 10.1016/0009-2797(93)90091-c.
For many acute-acting chemicals, toxic responses observed in vivo correlate strongly with metabolic activation and macromolecular covalent binding (CVB) observed in vitro and often in vivo; bromobenzene (BB) is a classic example of this behavior. Substituent groups modulate the toxicity of bromobenzene in vivo and in liver slices cultured in vitro in parallel fashion [Fisher, R., Hanzlik, R.P., Gandolfi, J.A., and Brendel, K. (1992), In Vitro Toxicology, 4, 173-186]. In the present study we used the liver slice system to examine the relationship between toxicity, metabolism and covalent binding amongst a series of [3H/14C] dual labelled BB derivatives including (in order of increasing hepatotoxicity) o-bromoanisole (BA), o-bromotoluene (BT), o-bromobenzonitrile (BBN), BB and o-dibromobenzene (DBB). Among these congeners apparent relative rates of metabolism varied only 4-fold, but the most extensively metabolized compounds were the least toxic. CVB varied 7-fold across the series, and those compounds which bound the most frequently were the most toxic. For each compound the relative binding index (RBI = pmol bound/nmol metabolized) and the average retention of tritium relative to carbon-14 in the CVB fraction were constant throughout the 24 h incubations, suggesting that the metabolic profile of each compound remained constant with time. The RBI values, however, did not reflect relative toxicity as well as total CVB values. The T/C ratios of the CVB residues varied from 0.36 (for BA) to 0.81 (for BBN), indicating that ortho-substitution on BB exerts important qualitative as well as quantitative effects on overall metabolism and reactive metabolite formation. The finding that relative toxicity among a series of bromobenzene congeners is paralleled by their relative covalent binding measured in the same system in which toxicity is assessed adds support to the hypothesis that covalent binding contributes to the observed toxicity, rather than merely being a correlated epiphenomenon.
对于许多急性作用的化学物质而言，体内观察到的毒性反应与体外乃至体内观察到的代谢活化和大分子共价结合（CVB）密切相关；溴苯（BB）就是这种情况的一个典型例子。取代基以平行方式调节溴苯在体内和体外培养的肝切片中的毒性[Fisher, R., Hanzlik, R.P., Gandolfi, J.A., and Brendel, K. (1992), In Vitro Toxicology, 4, 173 - 186]。在本研究中，我们使用肝切片系统来研究一系列[³H/¹⁴C]双标记溴苯衍生物（按肝毒性递增顺序包括邻溴苯甲醚（BA）、邻溴甲苯（BT）、邻溴苯腈（BBN）、溴苯（BB）和邻二溴苯（DBB））之间的毒性、代谢和共价结合关系。在这些同系物中，明显的相对代谢速率仅相差4倍，但代谢最广泛的化合物毒性最小。整个系列中CVB相差7倍，共价结合最频繁的那些化合物毒性最大。对于每种化合物，相对结合指数（RBI = 结合的皮摩尔数/代谢的纳摩尔数）以及CVB部分中氚相对于碳 - 14的平均保留率在整个24小时孵育过程中保持恒定，这表明每种化合物的代谢谱随时间保持恒定。然而，RBI值并未像总CVB值那样很好地反映相对毒性。CVB残留物的T/C比值从0.36（对于BA）到0.81（对于BBN）不等，表明溴苯上的邻位取代对整体代谢和活性代谢物形成产生重要的定性和定量影响。在评估毒性的同一系统中测量的一系列溴苯同系物的相对共价结合与其相对毒性平行，这一发现支持了共价结合导致观察到的毒性这一假设，而不仅仅是一种相关的附带现象。
