II. Effects Fecal Stream on DMH-Induced Colorectal Tumors in Rats

Abstract

It is well known from studies in rats that Dimethylhydrazine (DMH) administered subcutaneously is an effective carcinogen for large intestine.In this paper how fecal stream influence the pathogenesis of DMH induced colorectal tumor in rats (Donryu strain, male) was studied.The results of our experiments were as follows:1st. experiment: In the large bowel isolated completely from fecal stream, tumors were induced by administration subcutaneously of DMH, but frequency of induced tumors in these bowel was lower than in nonisolated large bowel. From these observation it is assumed that DMH or it's metabolites would reach the mucosa of large bowel not only via the biliary route and fecal stream, but also via blood stream.2nd. experiment: Tumors were also induced in the colon segment that transposed between choledochus and small intestine by subcutaneously administration of DMH.3rd. experiment: Right or left sided large bowel was isolated from fecal stream after DMH treatment. It was demonstrated that DMH-induced tumor was larger in size but smaller in number in the segment of the large bowel isolated from fecal stream than in the large bowel with fecal stream. It was suggested that normal fecal stream have some important effects upon incidence of induced tumors and growth of tumors.