Effects of sublethal irradiation on changes in crypts of the mouse colon during treatment with 1,2-dimethylhydrazine.
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.
D019813:1,2-Dimethylhydrazine; D000818:Animals; D001345:Autoradiography; D002273:Carcinogens; D002455:Cell Division; D003106:Colon / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects*; D003110:Colonic Neoplasms / Q000139:chemically induced*; D004127:Dimethylhydrazines / Q000633:toxicity*; D005260:Female; D007413:Intestinal Mucosa / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects; D008763:Methylhydrazines / Q000633:toxicity*; D051379:Mice; D009374:Neoplasms, Experimental / Q000139:chemically induced; D011230:Precancerous Conditions / Q000139:chemically induced*; D013997:Time Factors; D014916:Whole-Body Irradiation
D002273:Carcinogens; D004127:Dimethylhydrazines; D008763:Methylhydrazines; D019813:1,2-Dimethylhydrazine