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本实验应用二甲肼(DMH)给110只雌性昆明种小鼠皮下注射诱发大肠癌。在实验开始的42天将动物均分成对照、维生素A(VA)及维生素C(VC)三组、VA组动物隔日以3600iu灌胃,共24次,总量86400iu,VC组则每日饮入VC约83mg。在第6个半月处死全部存活小鼠,对其大肠作肉眼及显微镜检查。实验过程中,对照、VA、VC组总死亡率分别为43.2％,54.1％,22.2％。6.5个月大肠诱癌率为93.8％,66.7％及95.8％。诱发的大肠肿瘤数则为4.1±2.8,2.0±2.6,5.3±7.3。肛门以上8cm肠段重量为0.45±0.15,0.31±0.08,0.45±0.16g。实验期间体重的增长以VC最明显且较稳定,VA组在用药后74天下降明显。综上可见,长期服用超剂量VA可抑制DMH诱发大肠癌,但中毒严重。大量VC可减少死亡率,增加体重,但对DMH诱癌率及大肠肿瘤数与单用DMH者无差异。注射DMH的动物大肠细胞中~3H-TdR掺入DNA的量较正常细胞明显增加,但应用VA或VC后,并不能使其含量降低。
In this experiment, 110 female Kunming mice were injected subcutaneously with dimethylhydrazine (DMH) to induce colorectal cancer. Animals were divided into three groups: control, vitamin A (VA) and vitamin C (VC) at the beginning of the experiment. Animals in the VA group were intragastrically administered 3600iu every other day for a total of 24 doses (86400iu). The VC group was administrated daily. VC about 83mg. All surviving mice were sacrificed on the sixth and a half months, and the large intestine was visually and microscopically examined. During the experiment, the total mortality in the control, VA, and VC groups was 43.2%, 54.1%, and 22.2%, respectively. The 6.5-month colon cancer induction rate was 93.8%, 66.7% and 95.8%. The number of colorectal tumors induced was 4.1±2.8, 2.0±2.6, and 5.3±7.3. The 8 cm intestine weight above the anus was 0.45±0.15, 0.31±0.08, and 0.45±0.16 g. The increase in body weight during the experiment was most obvious and stable with VC, and the VA group decreased significantly after 74 days of treatment. In summary, overdose of VA over a long period of time may inhibit DMH-induced colorectal cancer, but the poisoning is severe. A large number of VC can reduce the mortality and increase the weight, but there is no difference between the DMH tumor-inducing rate and the number of colorectal tumors and DMH alone. The amount of ~3H-TdR-incorporated DNA in the large intestine cells injected with DMH was significantly higher than that of normal cells, but it could not be reduced by VA or VC.