REACTIVITY OF TISSUE-SPECIFIC ANTIGENS IN N-METHYL-N'-NITRO-N-NITROSOGUANIDINE-INDUCED NEOPLASMS AND NORMAL-TISSUES FROM MEDAKA (ORYZIAS-LATIPES)

To further characterize the distribution of tissue-specific antigens i n fish neoplasms, juvenile medaka were exposed to 30 mg/L of N-methyl- N'-nitro-N-nitrosoguanidine (MNNG) for 1 hr and allowed to grow out fo r up to 16 mo. Using a streptavidin peroxidase technique, keratin, vim entin, and neurofilament intermediate filament proteins, and actin and S-100 proteins were labeled in MNNG-induced neoplasms and normal meda ka tissues using specific monoclonal or polyclonal antibodies. In vasc ular tumors, rhabdomyosarcoma, and teratoma, muscle tissues were posit ive for actin. Other sarcomas including hemangiopericytoma, fascial sa rcoma, and undifferentiated sarcoma were negative for all antibodies t ested. An unusual scale-associated neoplasm, composed of clusters of s cale-forming cells surrounding spicules of scale, had keratin-positive stroma. The epithelial neoplasms were also positive for keratin, exce pt for pancreatic acinar carcinoma, which had limited positivity. Both teratoma and olfactory carcinoma had S-100-positive intraepithelial c ells morphologically reminiscent of neurosensory epithelial cells, whi ch were S-100 positive in normal tissues. Although positive reactivity in fish tissues correlated with mammalian data, the antibodies used w ere raised against mammalian antigens. Therefore, a negative reaction may be indicative of lack of antibody sensitivity to specific fish ant igens rather than absence of the antigen in the tissues. However, thes e data show that tissue-specific antigen detection may assist in eluci dating the biology of neoplasia in fish.