Relationship between experimental results in mammals and man. I. Cytogenetic analysis of bone marrow injury induced by a single dose of cyclophosphamide.

The extrapolation of experimental results to man was studied by cytogenetic bone marrow analysis and micronucleus test in mice, rats and Chinese hamsters. Furthermore, the frequency of chromosomal aberrations was compared with the frequencies of polychromatic erythrocytes containing micronuclei. Cyclophosphamide (CY) was given intraperitoneally at the doses of 5, 10, 20, 40 and 80 mg/kg b.w. to ICR mice and Wistar rats and at the doses of 10, 20, 40, 80, 120 and 160 mg/kg b.w. to Chinese hamsters. Five patients with various types of malignancies until then medically untreated, were i.v. administered 40 mg CY/kg b.w. Bone marrow cells were examined 24 h after the administration. CY induced in all rodents a clear-cut dose-effect relationship in the frequency of breaks, abnormal metaphases as well as in the frequency of micronuclei in polychromatic erythrocytes. When comparing the results in rodents and man at the dose of 40 mg CY/kg b.w., the sensitivity pattern of species was mice greater than rats greater than Chinese hamsters greater than man. From this aspect the possible differences in the metabolism of CY in analysed species are discussed. The presented results tend to a conclusion that micronucleus testing may be a very suitable method used for screening purpose, however, the method of classical cytogenetic analysis, especially the evaluation of breaks, still remains the most exact and reliable technique.