AbstractNineteen of the 209 possible polychlorinated biphenyl (PCB) congeners are chiral and stable to racemization at ambient temperature. Chiral PCB congeners are important components of technical and environmental PCB mixtures, and some are highly toxic. Both environmental and laboratory studies have shown that these chiral PCB congeners undergo enantiomeric enrichment in many species; however, the processes and factors influencing the extent of this enantiomeric enrichment are poorly understood. We hypothesized that the exposure levels are an important factor affecting the extent of enantiomeric enrichment. To test this hypothesis, we investigated the levels and enantiomeric fractions of (±)‐PCB 136 in selected tissues, feces, and urine of female C57Bl/6 mice 3 d after oral administration of 2.5, 10, or 50 mg/kg body weight of (±)‐PCB 136. The PCB 136 tissue levels typically increased with increasing dose. The extent of the enrichment of (+)‐PCB 136 in tissues and feces, however, decreased with increasing dose, an observation that suggests a saturation of the disposition process responsible for the enantiomeric enrichment. Overall, the present study demonstrates that in addition to species, exposure source, exposure frequency, and other factors, levels of PCB exposure are an important determinant of the enantiomeric enrichment of PCBs in mice and, most likely, other species.
摘要 209 种可能的多氯联苯(PCB)同系物中有 19 种是手性的,并且在环境温度下对消旋化稳定。手性多氯联苯同系物是技术和环境多氯联苯混合物的重要组成部分,其中一些具有剧毒。环境研究和实验室研究都表明,这些手性多氯联苯同系物在许多物种中都会发生对映体富集;然而,影响这种对映体富集程度的过程和因素却鲜为人知。我们假设,接触水平是影响对映体富集程度的一个重要因素。为了验证这一假设,我们研究了雌性 C57Bl/6 小鼠口服 2.5、10 或 50 毫克/千克体重的 (±)-PCB 136 3 天后,其特定组织、粪便和尿液中 (±)-PCB 136 的含量和对映体组分。多氯联苯 136 在组织中的含量通常会随着剂量的增加而增加。然而,组织和粪便中 (+)-PCB 136 的富集程度随着剂量的增加而降低,这一观察结果表明对映体富集的处置过程已经饱和。总之,本研究表明,除了物种、接触源、接触频率和其他因素外,多氯联苯的接触水平也是小鼠以及很可能其他物种体内多氯联苯对映体富集的重要决定因素。