Abstract

• The fact that the administration of 1,2-dimethylhydrazine 2Hcl(DMH) to rats by weekly subcutaneous injections causes the development of epithelial tumors of the large intestine has been known. But the axact processes of of early morphologic changes of colonic lesion induced by DMH treatment in the rats have not been fully testified as yet. The objective of the dissertation research is to examine early morphologic changes of colonic lesion induced by DMH treatment in the rats. Total seventy cases including 14 control rats of Sprague Dawley male rats were analyzed by histopathologic changes. One is 20mg/kg/wk DMH treated rat group and the other is 40mg/kg/wk DMH treated rat group. DMH was injected s.c. at the start of each treatment weekly during 20 weeks, and the animals were killed at 1, 3, 5, 6, 7, 9, 12, 14, 17 or 20 weeks both in 20mg/kg/wk DMH treated group and in 40mg/kg/wk DMH treated group. The following results were obtained: Hyperplasia and mitosis of the crypt are presented in early phase of DMH treatment. Cellular dysplasia, carcinoma in situ, and invasive carcinoma are shown in later phase of DMH treatment. The same changes as the above are also identified in electron microscopic findings. The more doses of DMH are injected to rats, the more evident these findings are presented. The alkaline phosphatase activity in glandular epithelial cells are observed in cellular dysplasia and neoplastic changes. The alkaline phosphatase may be considered as tumor marker.