Shane B S, Lockhart A M, Winston G W, Tindall K R
Institute for Environmental Studies, Louisiana State University, Baton Rouge 70803, USA.
Mutat Res. 1997 Jun 9;377(1):1-11. doi: 10.1016/s0027-5107(97)00004-3.
The Big Blue, transgenic mouse provides an in vivo mutation system that permits the study of pharmacodynamic parameters on mutant frequency (MF) following xenobiotic exposure. We have studied the effects of cellular proliferation on the frequency of mutations in the lacl transgene by evaluating the MF in the liver of male C57B1/6 Big Blue mice following treatment with benzo[a]pyrene (B[a]P) and a partial hepatectomy. Mice received either 40 mg/kg of B[a]P in corn oil or corn oil alone by i.p. injection on three consecutive days, followed by a partial hepatectomy on the fourth day. Three days later (i.e., 7 days following the initial B[a]P injection), the animals were sacrificed and the MF in the liver was compared to the MF observed in the liver of the same mouse at the time of hepatectomy. Induction of cytochrome P-450 1A (CYP1A) following B[a]P treatment was evident by Western blot analysis. The MF in untreated control animals was not significantly different at hepatectomy (4.7 +/- 0.8 x 10(-5)) and 3 days later, at sacrifice (3.0 +/- 0.4 x 10(-5)). Neither was the MF observed in the B[a]P-treated mice at the time of sacrifice (12.0 +/- 2.1 x 10(-5)) significantly different from the MF observed at the time of hepatectomy (10.6 +/- 5.3 x 10(-5)). However, B[a]P-treatment resulted in a 4.0-fold increase in MF at sacrifice which was significantly different (p < 0.05), when compared to the untreated controls. The B[a]P-treated mice at hepatectomy showed a modest 2.2-fold increase in MF which was not statistically significantly different from the untreated controls. In addition, both control and B[a]P-treated tissues gave sectored mutant plaques. The sectored plaque frequency (SPF) was significantly elevated (p < 0.05) in the B[a]P-treated mice at hepatectomy (4.2 +/- 1.0 x 10(-5)) and sacrifice (7.3 +/- 2.4 x 10(-5)) as compared to the respective frequency in the control mice at hepatectomy (1.9 +/- 0.7 x 10(-5)) and sacrifice (1.4 +/- 0.2 x 10(-5)). One explanation for this data is the persistence of the B[a]P adducts in the mouse genomic DNA that was packaged into the lambda phage, and ultimately fixed as mutations in Escherichia coli.
“大蓝”转基因小鼠提供了一种体内突变系统，可用于研究外源化合物暴露后对突变频率（MF）的药效学参数。我们通过评估苯并[a]芘（B[a]P）处理和部分肝切除术后雄性C57B1/6“大蓝”小鼠肝脏中的MF，研究了细胞增殖对lacl转基因突变频率的影响。小鼠连续三天腹腔注射40mg/kg溶于玉米油的B[a]P或仅注射玉米油，第四天进行部分肝切除术。三天后（即首次注射B[a]P后7天），处死动物，将肝脏中的MF与肝切除时同一小鼠肝脏中观察到的MF进行比较。通过蛋白质印迹分析可知，B[a]P处理后细胞色素P-450 1A（CYP1A）的诱导明显。未处理的对照动物在肝切除时（4.7±0.8×10⁻⁵）和三天后处死时（3.0±0.4×10⁻⁵）的MF无显著差异。B[a]P处理的小鼠在处死时观察到的MF（12.0±2.1×10⁻⁵）与肝切除时观察到的MF（10.6±5.3×10⁻⁵）也无显著差异。然而，与未处理的对照组相比，B[a]P处理导致处死时MF增加了4.0倍，差异显著（p<0.05）。B[a]P处理的小鼠在肝切除时MF适度增加了2.2倍，与未处理的对照组相比无统计学显著差异。此外，对照组织和B[a]P处理的组织均出现了扇形突变噬菌斑。与肝切除时（1.9±0.7×10⁻⁵）和处死时（1.4±0.2×10⁻⁵）对照小鼠的相应频率相比，B[a]P处理的小鼠在肝切除时（4.2±1.0×10⁻⁵）和处死时（7.3±
