石英对大鼠肺上皮细胞和成纤维细胞的增殖抑制及致hprt基因突变的研究

目的探讨石英对大鼠肺泡II型上皮细胞和成纤维细胞的增殖抑制及致hprt基因突变的差异。方法采用(MTT噻唑蓝)比色法检测大鼠肺成纤维细胞和肺泡II型上皮细胞的增殖抑制毒性。以含6-巯基鸟嘌呤(6-TG)的培养基筛选突变细胞克隆,检测hprt基因突变频率。结果在相同的染毒条件下,肺泡II型上皮细胞对石英刺激比成纤维细胞更易受损伤,上皮细胞半数增殖抑制浓度(IC50)约为140μg/cm2,成纤维细胞的IC50约为282μg/cm2。在致hprt基因突变方面,石英粉尘对两种细胞都有致突变作用。在同样剂量染毒条件下,肺泡Ⅱ型上皮细胞的hprt突变频率为84.2×10-6～156.6×10-6,较成纤维细胞(67.6×10-6～114.3×10-6)更容易发生hprt基因突变,差异有显著性(P<0.05)。结论石英对大鼠肺成纤维细胞和肺泡II型上皮细胞的细胞毒性及对hprt基因致突变作用强度存在明显差异。肺泡II型上皮细胞对石英刺激的反应敏感性高于成纤维细胞。

Study on the silica-induced cytotoxicity and hprt gene mutagenisis in rat lung fibroblasts and alveolar type Ⅱ epithelial cells

OBJECTIVE: To explore the differences of the silica-induced inhibition on cellular proliferation and hprt gene mutagenesis between lung fibroblasts and alveolar type II cells. METHODS: The proliferation inhibitive cytotoxicity was detected by MTT (3-[4,5-Dimethylthiazolzyl]-2,5-Diphenyl Tetrazolium Bromide) colorimetric method. Mutation in the hprt gene was screened by culture in the presence of the toxic purine analog, 6-thioguanine (6-TG). RESULTS: Under the same circumstances of silica exposure, alveolar type II cells was more sensitive than lung fibroblasts for proliferation inhibition. The median proliferation inhibition concentration (IC50) of silica on epithelial was 140 micrograms/cm2, whereas IC50 of silica on fibroblasts was 282 micrograms/cm2. At the same doses of silica, the hprt gene mutation frequency in type II cells (84.2 x 10(-6))-156.6 x 10(-6) was statistically higher than that in fibroblasts (67.6 x 10(-6)-114.3 x 10(-6), P < 0.05). CONCLUSION: There were significant differences of both silica-induced cell proliferation inhibition and hprt gene mutation between rat lung fibroblasts and type II epithelial cells. In vitro, cultured rat alveolar type II cells were more sensitive in cytotoxicity and hprt gene mutagenesis to silica dust than lung fibroblasts were.