STABILITY OF THE TRANSLOCATION FREQUENCY FOLLOWING WHOLE-BODY IRRADIATION MEASURED IN RHESUS-MONKEYS

Chromosome translocations are persistent indicators of prior exposure to ionizing radiation and the development of 'chromosome painting' to efficiently detect translocations has resulted in a powerful biologica l dosimetry tool for radiation dose reconstruction. However, the actua l stability of the translocation frequency with time after exposure mu st be measured before it can be used reliably to obtain doses for indi viduals exposed years or decades previously. Human chromosome painting probes were used here to measure reciprocal translocation frequencies in cells from two tissues of 8 rhesus monkeys (Macaca mulatta) irradi ated almost three decades previously. Six of the monkeys were exposed in 1965 to whole-body (fully penetrating) radiation and two were unexp osed controls. The primates were irradiated as juveniles to single dos es of 0.56, 1.13, 2.00, or 2.25 Gy. Blood lymphocytes (and skin fibrob lasts from one individual) were obtained for cytogenetic analysis in 1 993, near the end of the animals' lifespans. Results show identical do se-response relationships 28 y after exposure in vivo and immediately after exposure in vitro. Because chromosome aberrations are induced wi th identical frequencies in vivo and in vitro, these results demonstra te that the translocation frequencies induced in 1965 have not changed significantly during the almost three decades since exposure. Finally , our emerging biodosimetry data for individual radiation workers are now confirming the utility of reciprocal translocations measured by FI SH in radiation dose reconstruction.