Tice R R, Furedi-Machacek M, Satterfield D, Udumudi A, Vasquez M, Dunnick J K
Integrated Laboratory Systems, Research Triangle Park, North Carolina, USA.
Environ Mol Mutagen. 1998;31(2):113-24. doi: 10.1002/(sici)1098-2280(1998)31:2<113::aid-em3>3.0.co;2-n.
Phenolphthalein, a common ingredient in nonprescription laxatives and a multisex, multispecies rodent carcinogen, was evaluated under chronic exposure conditions for genotoxicity in transgenic female mice heterozygous for the p53 gene (heterozygous TSG-p53 mice). Phenolphthalein was administered in the diet at 200, 375, 750, 3,000, and 12,000 ppm (corresponding to a time-weighted average of 37, 71, 146, 569, and 2,074 mg/kg/day, respectively) for 6 months (183 days). On days 39, 92, 137, and 183 of treatment, peripheral blood samples were collected and evaluated for the frequency of micronucleated polychromatic and normochromatic erythrocytes (MN-PCE and MN-NCE, respectively), the percentage of PCE (%PCE) among total erythrocytes, and the extent of DNA damage (single strand breaks, alkali labile sites, DNA crosslinking) in leukocytes. In addition, the extent of DNA damage was evaluated in liver parenchymal cells sampled from mice at the end of the 6-month treatment period. DNA damage was evaluated using the alkaline (pH > 13) Single Cell Gel (SCG) assay. In addition, using a modified SCG technique, the frequencies of leukocytes and liver parenchymal cells with extremely low molecular weight DNA (indicative of apoptosis and/or necrosis) were determined. At each sample time, phenolphthalein induced a highly significant, dose-dependent increase in the frequency of MN-PCE and MN-NCE and in %PCE. Maximal induction of MN-PCE and %PCE decreased with increasing treatment duration, most likely due to a treatment duration-dependent decrease in the relative amount of ingested phenolphthalein. A comparative analysis of the kinetochore status of MN in erythrocytes sampled from control mice and mice ingesting phenolphthalein at 12,000 ppm for 183 days indicates that the induced MN resulted predominantly but not exclusively from numerical chromosomal damage. The analysis for increased levels of DNA damage in blood leukocytes was inconclusive, with a small but statistically significant increase in DNA migration on days 39 and 137 but not on days 92 and 183. The extent of DNA migration in liver parenchymal cells sampled from mice at the end of treatment was not altered significantly. The frequencies of apoptotic and/or necrotic leukocytes and liver parenchymal cells were not increased among mice ingesting phenolphthalein. The lowest effective dose at which a significant genotoxic response (i.e., the induction of MN-NCE) was detected was 200 ppm, the lowest dose tested in this study. This dose in mice is comparable to doses (on a mg/m2 basis) experienced by humans.
酚酞是一种非处方泻药中的常见成分，也是一种对多种性别、多种物种的啮齿动物具有致癌性的物质。本研究在慢性暴露条件下，对p53基因杂合的转基因雌性小鼠（杂合TSG-p53小鼠）进行了酚酞遗传毒性评估。将酚酞以200、375、750、3000和12000 ppm的浓度添加到饲料中（分别相当于时间加权平均剂量为37、71、146、569和2074 mg/kg/天），持续6个月（183天）。在处理的第39、92、137和183天，采集外周血样本，评估多染性红细胞和正染性红细胞的微核频率（分别为MN-PCE和MN-NCE）、总红细胞中PCE的百分比（%PCE）以及白细胞中的DNA损伤程度（单链断裂、碱不稳定位点、DNA交联）。此外，在6个月处理期结束时，对从小鼠采集的肝实质细胞中的DNA损伤程度进行了评估。使用碱性（pH>13）单细胞凝胶（SCG）试验评估DNA损伤。此外，使用改良的SCG技术，测定了极低分子量DNA的白细胞和肝实质细胞的频率（指示凋亡和/或坏死）。在每个采样时间，酚酞均诱导MN-PCE和MN-NCE频率以及%PCE高度显著、剂量依赖性增加。MN-PCE和%PCE的最大诱导率随处理时间延长而降低，这很可能是由于摄入酚酞的相对量随处理时间延长而减少所致。对对照组小鼠和摄入12000 ppm酚酞183天的小鼠的红细胞中微核的动粒状态进行的比较分析表明，诱导产生的微核主要但并非完全由染色体数目损伤引起。对血液白细胞中DNA损伤水平升高的分析尚无定论，在第39天和137天DNA迁移有小幅但具有统计学意义的增加，而在第92天和183天则没有。处理结束时从小鼠采集的肝实质细胞中的DNA迁移程度没有显著改变。摄入酚酞的小鼠中凋亡和/或坏死的白细胞和肝实质细胞的频率没有增加。检测到显著遗传毒性反应（即诱导MN-NCE）的最低有效剂量为200 ppm，这是本研究中测试的最低剂量。小鼠中的这个剂量与人类接触的剂量（以mg/m2为基础）相当。
