1-2 Dimethylhydrazine induced colonic tumours in rats.

1-2 dimethylhydrazine was injected subcutaneously on a weekly basis of 15 mg/kg, during periods ranging from one to twenty-eight weeks into five hundred Wistar rats. Glandular-mucin depletion appears as early as the second injection (sulfomucins disappear). From the sixth week, one observes dysplasia; if the animals are allowed to survive for a longer period all will develop colonic carcinomas, which were found mainly in the left colon. This dysplasia, which is first mild, then moderate, is finally severe in rat mucosa or in the area of polyps. Dysplastic polyps become less frequent when carcinomas increase in number and in size. The average length of survival after cessation of the exposure is inversely proportional to the total dose administered. The glandular mucin depletion-dysplasia-carcinoma sequence characterizes the types of formation of 1-2 DMH induced colonic carcinomas. One of the striking features is the early appearance of this sequence.