Detection of total- and partial-body irradiation in a monkey model:: a comparative study of chromosomal aberration, micronucleus and premature chromosome condensation assays

Purpose: To investigate the efficacy of three cytogenetic methods (dicentrics, micronuclei (MN) and premature chromosome condensation (PCC) analysis) for assessment of the unirradiated fraction and the persistence of damage after total-body (TB) and partial-body (PB) irradiation of rhesus monkeys (Macaca mulatta). Materials and methods: Animals were exposed to X-rays (5 Gy), either TB or PB, with about 6% of marrow cells shielded. Blood samples were collected at different rimes after exposure, i.e. 1, 3 and 7 days, and cultures were set up for the different cytogenetic endpoints. In addition, blood count analysis was performed before and after irradiation. Results: Blood count analysis was not suitable for discriminating between TB and PB exposure. By using Poisson or overdispersion distribution as the basis, it was not possible to distinguish TB from PB irradiation when dicentric chromosomes and MN were analysed. PCC analysis, in contrast, showed a Poisson distribution after TB exposure and overdispersion after PB exposure. Using the PCC assay, reliable dose estimates could be obtained up to 7 days after irradiation. Conclusions: For dicentrics and MN, shielding of 6% of bone marrow cells was found to be too small to estimate the unirradiated fraction accurately. The PCC technique was useful for dose assessment and the inhomogeneous exposure of 6% was detected within a short period of time after exposure.