Effect of N-methyl-N'-nitro-N-nitrosoguanidine on immune response in rats in stomach carcinogenesis

Subcutaneous injections of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) at the dose of 50 mg/kg body weight for 10 days showed depressed production of hemolysin against sheep red blood cells (SRNC) in Wistar rats. On the other hand, oral administration at the dose of approximately 35 mg/kg body weight for 30 weeks scarcely suppressed antibody preduction to heterologous RBC and cell-mediated immune response to Walker-256 carcinosarcoma in Wistar rats during the experimental period of 55 weeks. The daily administration by way of oral route proved to be efficient for the induction of stomach cancer. The difference in immunosuppressive effect of MNNG by these two routes will be discussed in relation to the susceptibility of in vivo degradation of the carcinogen.