J.Jpn. Surg. Soc.. 87(6): 626-635, 1986

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Original article

SERIAL ENDOSCOPIC EXAMINATIONS OF 1,2-DIMETHYLHYDRAZINE INDUCED COLON TUMORS IN RAT AND EFFECTS OF FECAL STREAM

Some new aspects regarding 1, 2-dimethylhydrazine induced rat colon tumors were obtaned from the findings of weekly endoscopic examinations of induced tumors and their histological results. It was observed endoscopically that each tumor had a different speed of growth. There was no relation between the time when a tumor appeared and the depth of its invasion at sacrifice. Biopsies were taken from several tumors at an early stage when these tumors were recognized endoscopically. The histological findings of the biopsy specimens were all compatible with adenocarcinoma. The total number of tumors increased with time.
As a second step, the effect of fecal stream upon the carcinogenesis in rats of our experimental model was investigated by periodic endoscopy before and after fecal diversion, and by histological examination. Without a fecal stream microscopic foci of atypical glands did not grow to become visible tumors. However, a tumor which had already become visible in endoscopy grew in the absence of a fecal stream. It is possible to say that the carcinogenesis of this experimental model has two distinct phases, i.e., initiation and promotion. Our result could give valuable information for the study of carcinogenesis in human large bowel.

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