The mutagenic activity of aflatoxin B1 in the Cricetulus griseus hamster and Macaca mulatta monkey

Chromosome aberrations were scored in bone marrow cells of Cricetulus griseus hamsters and Macaca mulatta monkeys given a single i.p. injection of aflatoxin B1 (AFB1). The mutagenic activity of AFB1 was assessed by the percentage of cells bearing aberrations and by the total frequency of chromosome and chromatid breaks. Chinese hamsters were treated with five different doses of AFB1 ranging from 1 microgram to 5 mg/kg (LD50/30 = 12.2 mg/kg) and the aberration yields at each AFB1 dose level tested were determined at 24 h intervals for 5 consecutive days. Compared to controls the increase in the two types of chromosome abnormalities was significant in all tests. At 5 mg/kg of AFB1 the tests were carried out over a period of 92 days to assure the analysis of aberration yields with time. All chromosome aberration assays conducted during this period showed significant increases in the frequencies of aberrant cells and chromosome and chromatid breaks in comparison to controls. Macaque monkeys were treated in the same fashion using 0.1 and 1.0 mg/kg of AFB1 and the dynamics of chromosome aberration yields was analyzed for a period of 730 days. Similarly as in the case of Chinese hamsters the percentage of cells with aberrations and the frequency of chromosome and chromatid breaks were always higher in this period than the control value. Long-term aberration yield data obtained experimentally were expressed in the form of analytical curves which allowed to establish the time when the yields of aberrant cells reached their maxima and when they returned to the control level. In both animal species tested the courses of analytical curves had a similar dynamics. Factors that might be responsible for a long-term persistence and relatively great fluctuations of the chromosome aberration yields encountered after a single injection of AFB1 are discussed in detail.