Richards T C, Tacha D E
J Natl Cancer Inst. 1982 Sep;69(3):693-7.
The effects of low-dose X-irradiation on the progression of early neoplastic changes induced in the colon by 1,2-dimethylhydrazine (DMH) were assessed. Outbred female Swiss-Webster mice were treated with DMH only, DMH-irradiation, irradiation only, or 0.001 M EDTA. Animals were pulsed with [3H]thymidine for 1 hour, and the distal colon was radioautographed. The number of labeled cells per crypt in animals tested with DMH-irradiation was greater (P less than 0.01) than the number in "DMH-only" animals, but a corresponding increase in the length of the crypts did not occur. After 16 weeks of treatment, the percentage of animals with focal atypia was similar in the DMH-irradiation group (87%), and the DMH-only group (100%), but there were more focal atypias per animal in the DMH-only group. After 20 weeks, 14% of the DMH-irradiation group had visible tumors compared to 63% of the DMH-only group. The results suggest that DMH increased the number of cells at risk for irradiation; thus the surge in proliferation subsequent to cell depletion was amplified. However, the development of precancerous lesions was not promoted.
评估了低剂量X射线照射对1,2 - 二甲基肼（DMH）诱导的结肠早期肿瘤性变化进展的影响。远交系雌性瑞士韦伯斯特小鼠分别接受仅DMH处理、DMH - 照射处理、仅照射处理或0.001 M乙二胺四乙酸（EDTA）处理。给动物注射[³H]胸腺嘧啶1小时，然后对结肠远端进行放射自显影。接受DMH - 照射处理的动物中每个隐窝标记细胞的数量比“仅DMH处理”的动物多（P小于0.01），但隐窝长度没有相应增加。处理16周后，DMH - 照射组（87%）和仅DMH处理组（100%）中出现局灶性异型增生的动物百分比相似，但仅DMH处理组中每只动物的局灶性异型增生更多。20周后，DMH - 照射组有14%出现可见肿瘤，而仅DMH处理组为63%。结果表明，DMH增加了受照射风险的细胞数量；因此，细胞耗竭后增殖的激增被放大。然而，癌前病变的发展并未得到促进。
