title: Higher susceptibility to N-methyl-N'-nitro-N-nitrosoguanidine-induced tumorigenesis in an interstrain hybrid of the fish, Oryzias latipes (medaka).
abstract: Adult fish of an interstrain hybrid (F1) of inbred medaka, obtained from crosses between HO4C and HB32C, were exposed for 2 hr to an aqueous solution of the carcinogen N-methyl-N'-nitro-N-nitrosoguanidine at concentrations of 15, 20, 25, 30, and 35 ppm. Survival and neoplastic changes were examined over a 6-month period. A large variety of neoplasms were induced, including melanoma, papilloma, ovarian tumors, olfactory epithelioma, branchioblastoma and fibroma. More than 60% of the tumors were classified as melanoma on the basis of histological examinations. A markedly higher cumulative incidence of the melanoma with a dose-related response was demonstrated in the F1 hybrid fish compared to the parental strains. The latent period for melanoma development, however, remained unchanged in F1 compared to the parents. The variety of tumors induced in the F1 fish was greater than in the parental strains. The results indicate the usefulness of F1 hybrid fish in testing the carcinogenicity of certain water-soluble chemicals, due to their high sensitivity.
mesh_terms: D000818:Animals; D005260:Female; D006824:Hybridization, Genetic; D008297:Male; D008545:Melanoma / Q000139:chemically induced / Q000235:genetics*; D008769:Methylnitronitrosoguanidine; D009990:Oryzias
chemical_list: D008769:Methylnitronitrosoguanidine