Reduced levels of mutagen processing potential in the Schistosoma japonicum-infected mouse liver

Epidemiological studies have shown the presence of a positive correlation between the infection of Schistosoma japonicum and colorectal and/or liver cancers in the humans. To explore the mechanism underlying this correlation, we have investigated the mutagen-activating potentials of the liver homogenate fraction (S9) from Schistosoma japonicum infected mice and those from control mice, by use of the Ames test with 2-acetylaminofluorene, aflatoxin B₁ and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) as test mutagens. Liver S9 prepared from the infected group at the 15th week after the infection showed a potential significantly lower than that from the control group. The hepatic cytochrome P-450 concentration in the infected mice was persistently low, about a half of that in the uninfected mice, during the period of 6-18 weeks after the infection. Thus, in mice bearing chronic schistosomiasis, mutagen-processing potentials are decreased.