title: Effects of weaning by surrogate mothers (ACI) on tumor development in SD rats treated with methylnitrosourea (MNU) and/or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG).
abstract: In this experiment, methylnitrosourea (MNU) was administered, followed by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), to assess effects of surrogate mothering on tumor. One or two day old male SD pups were treated with or without 30 mg/kg body weight of MNU and nursed by SD or ACI surrogate mothers for 5 weeks. When 6-weeks-old they were then treated with 100 ppm MNNG or tap water for 16 weeks. The tumor incidence in the MNNG alone group was significantly lower than with MNU alone or MNU+MNNG (p < 0.01). Kidney or nerve tumors mainly developed in the MNU group, gastric tumors in the MNNG group, and the two combined in the MNU+MNNG group. The incidence and mean number of tumors did not significantly differ between the two weaning groups. However, mean survival time with the ACI surrogate mothers after treatment with MNU was increased as compared with the SD mother group. Cumulative development of tumors in the ACI surrogate mother group was also delayed (p < 0.05). Similar results were obtained with MNU+MNNG and MNNG alone. The present experiment suggested that tumor induction might be effected by components of the mother's milk.
authors.affiliation: Department of Cellular Biology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Shiraki
authors.forename: Huimei
authors.initials: H
authors.lastname: Lu
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Ishimura
authors.forename: Shoji
authors.initials: S
authors.lastname: Kashiwabara
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Uesaka
authors.forename: Osamu
authors.initials: O
authors.lastname: Katoh
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Watanabe
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D002273:Carcinogens / Q000633:toxicity; D005260:Female; D008297:Male; D008769:Methylnitronitrosoguanidine / Q000633:toxicity; D008770:Methylnitrosourea / Q000633:toxicity; D008892:Milk / Q000502:physiology*; D009374:Neoplasms, Experimental / Q000139:chemically induced / Q000209:etiology*; D051381:Rats; D011912:Rats, Inbred ACI; D017207:Rats, Sprague-Dawley; D013045:Species Specificity
chemical_list: D002273:Carcinogens; D008769:Methylnitronitrosoguanidine; D008770:Methylnitrosourea