title: Effects of X-irradiation on N-methyl-N-nitrosourea-induced multi-organ carcinogenesis in rats.
abstract: The effects of X-irradiation on N-methyl-N-nitrosourea (MNU)-induced multi-organ carcinogenesis were examined in both sexes of ACI/N rats. At 6 weeks of age, rats in groups 1 (25 males, 25 females) and 3 (24 males, 23 females) received a single i.p. injection of MNU (25 mg/kg body weight), while those in groups 2 (25 males, 26 females) and 4 (25 males, 25 females) were administered the carcinogen at a dose of 50 mg/kg body weight. At 10 weeks of age, groups 3 and 4 were X-irradiated at a dose of 3 Gy. Group 5 (24 males, 24 females) received X-irradiation alone. Group 6 (21 males, 21 females) served as an untreated control. As a result, neoplasms developed mainly in the digestive tract, kidney, uterus, and hematopoietic organ in groups 1-5. The incidences of adenocarcinoma in small and large intestines of male rats of group 4 (50 mg/kg MNU and X-irradiation) (small intestine: 48%, large intestine: 32%) were significantly higher than those of group 2 (50 mg/kg MNU) (small intestine: 17%, P < 0.05; large intestine: 8%, P < 0.05), and also the frequency of adenocarcinoma in the large intestine of males of group 3 (25 mg/kg MNU and X-irradiation) (22%) was significantly greater than that of group 1 (25 mg/kg MNU) (0%, P < 0.05). These results indicated that X-irradiation enhanced the development of intestinal neoplasms induced by MNU in male ACI/N rats.
authors.affiliation: First Department of Pathology, Gifu University School of Medicine.
authors.forename: Y
authors.initials: Y
authors.lastname: Morishita
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: H
authors.initials: H
authors.lastname: Mori
authors.forename: S
authors.initials: S
authors.lastname: Sasaki
mesh_terms: D000230:Adenocarcinoma / Q000139:chemically induced / Q000473:pathology; D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000528:radiation effects; D004067:Digestive System Neoplasms / Q000139:chemically induced / Q000473:pathology; D005260:Female; D007680:Kidney Neoplasms / Q000139:chemically induced / Q000473:pathology; D008297:Male; D008770:Methylnitrosourea / Q000633:toxicity*; D009374:Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology; D009381:Neoplasms, Radiation-Induced / Q000473:pathology*; D009929:Organ Size / Q000187:drug effects / Q000528:radiation effects; D051381:Rats; D011912:Rats, Inbred ACI; D012727:Sex Characteristics; D014594:Uterine Neoplasms / Q000139:chemically induced / Q000473:pathology; D014965:X-Rays
chemical_list: D008770:Methylnitrosourea