Smith-Kielland A, Ripel A
National Institute of Forensic Toxicology, Oslo, Norway.
Arch Toxicol. 1993;67(2):107-12. doi: 10.1007/BF01973680.
Hepatocytes isolated from control, acetone- and phenobarbital-pretreated rats were used to study the metabolic conversion of toluene to benzyl alcohol, benzaldehyde, benzoic acid and hippuric acid at low (< 100 microM) and high (100-500 microM) toluene concentrations. The baseline formation rates of toluene metabolites (benzyl alcohol, benzoic acid and hippuric acid) were 2.9 +/- 1.7 and 10.0 +/- 2.3 nmol/mg cell protein/60 min at low and high toluene concentrations, respectively. In vivo pretreatment of rats with acetone and phenobarbital increased the formation of metabolites: at low toluene concentrations 3- and 5-fold, respectively; at high toluene concentrations no significant increase (acetone) and 8-fold increase (phenobarbital). Apparent inhibition by ethanol, 7 and 60 mM, was most prominent at low toluene concentrations: 63% and 69%, respectively, in control cells; 84% and 91% in acetone-pretreated cells, and 32% (not significant) and 51% in phenobarbital-pretreated cells. Ethanol also caused accumulation of benzyl alcohol. The apparent inhibition by isoniazid was similar to that of ethanol at low toluene concentrations. Control and acetone-pretreated cells were apparently resistant towards metyrapone; the decrease was 49% and 64% in phenobarbital-pretreated cells at low and high toluene concentrations, respectively. In these cells, the decrease in presence of combined ethanol and metyrapone was 95% (low toluene concentrations). 4-Methyl-pyrazole decreased metabolite formation extensively in all groups. Benzaldehyde was only found in the presence of an aldehyde dehydrogenase inhibitor. Increased ratio benzoic/hippuric acid was observed at high toluene concentrations. These results demonstrate that toluene oxidation may be studied by product formation in isolated hepatocytes. However, the influence of various enzymes in the overall metabolism could not be ascertained due to lack of inhibitor specificity.
从对照、丙酮和苯巴比妥预处理的大鼠中分离出肝细胞，用于研究在低（<100微摩尔）和高（100 - 500微摩尔）甲苯浓度下，甲苯向苯甲醇、苯甲醛、苯甲酸和马尿酸的代谢转化。在低和高甲苯浓度下，甲苯代谢物（苯甲醇、苯甲酸和马尿酸）的基线生成速率分别为2.9±1.7和10.0±2.3纳摩尔/毫克细胞蛋白/60分钟。大鼠经丙酮和苯巴比妥进行体内预处理后，代谢物的生成增加：在低甲苯浓度下分别增加3倍和5倍；在高甲苯浓度下，丙酮处理组无显著增加，苯巴比妥处理组增加8倍。7和60毫摩尔的乙醇产生的明显抑制作用在低甲苯浓度时最为显著：在对照细胞中分别为63%和69%；在丙酮预处理的细胞中为84%和91%；在苯巴比妥预处理的细胞中为32%（不显著）和51%。乙醇还导致苯甲醇积累。在低甲苯浓度下，异烟肼的明显抑制作用与乙醇相似。对照和丙酮预处理的细胞对甲吡酮明显有抗性；在低和高甲苯浓度下，苯巴比妥预处理的细胞中代谢物生成的减少分别为49%和64%。在这些细胞中，乙醇和甲吡酮联合存在时代谢物生成的减少为95%（低甲苯浓度）。4 - 甲基吡唑在所有组中均广泛降低代谢物生成。仅在存在醛脱氢酶抑制剂时才发现苯甲醛。在高甲苯浓度下观察到苯甲酸/马尿酸的比例增加。这些结果表明，甲苯氧化可通过分离肝细胞中的产物生成来研究。然而，由于缺乏抑制剂特异性，无法确定各种酶在整体代谢中的影响。
