The effects of different MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) doses on the stomach and the upper small intestine of the rat. I. The frequency and histopathology of the induced tumours.
N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was given to 3 groups of rats with the drinking water for 32 weeks in different doses: 25, 50 and 100 micrograms/ml. After 50 weeks the induced tumours of the stomach and the upper small intestine were investigated. Most tumours were well differentiated adenocarcinomas or adenomatous-hyperplastic lesions with focal adenocarcinoma. After low MNNG-concentration (25 micrograms/ml) only adenomatous hyperplastic lesions with focal adenocarcinoma were found. A tumour development in connection with intestinal metaplasia was detectable exclusively in two rats of the group receiving 50 micrograms MNNG/ml. The frequency of gastric tumours shows a relatively low peak (3.3 tumours/10 animals) after administering a medium MNNG-concentration (50 micrograms/ml) and a little decrease of the frequency after higher MNNG-concentration, as opposed to the approximately linear dose-related increase of the tumour frequency in the upper small intestine. The highest tumour induction rate was found in the upper small intestine after 100 micrograms MNNG/ml (5.6 tumours/10 rats). It can be concluded that the mucosa of the upper small intestine possesses a greater susceptibility to the carcinogenic effect of MNNG than the glandular stomach of the rat.
D000230:Adenocarcinoma / Q000139:chemically induced* / Q000473:pathology; D000284:Administration, Oral; D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006965:Hyperplasia; D007414:Intestinal Neoplasms / Q000139:chemically induced* / Q000473:pathology; D007421:Intestine, Small / Q000473:pathology; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000008:administration & dosage / Q000633:toxicity*; D009361:Neoplasm Invasiveness; D051381:Rats; D011919:Rats, Inbred Strains; D013270:Stomach / Q000473:pathology; D013274:Stomach Neoplasms / Q000139:chemically induced* / Q000473:pathology
D008769:Methylnitronitrosoguanidine