Easy biodosimetry for high-dose radiation exposures using drug-induced, prematurely condensed chromosomes

PURPOSE: To propose a practical method of biodosimetry for high-dose estimation. MATERIALS AND METHODS: Okadaic acid in the range 100 nM to 500 nM was given for 1-6 h to cultured lymphocytes that had been exposed in the range of 0 Gy to 40 Gy. The frequency of the cells with prematurely condensed chromosomes (PCC) was compared with that of metaphases accumulated by 0.05 microg/ml colcemid. The dose-response relationship of the yield of prematurely condensed ring chromosomes (PCC rings) in the irradiated lymphocytes was examined. RESULTS: The 0.05 microg/ml colcemid collected few metaphases when lymphocytes were irradiated to over 10 Gy. However, 500 nM okadaic acid produced a substantial number of analysable PCC in lymphocytes that had been exposed in the range of 0 Gy to 40 Gy. After 1 h of treatment, the 500 nM okadaic acid gave the most suitable chromosome morphology for the analysis. PCC rings were narrow, which facilitated their detection in Giemsa-stained preparations. The yield of PCC rings increased dose-dependently up to 20 Gy. CONCLUSION: PCC rings are a more suitable indicator than dicentrics at high doses over 10 Gy. This technique requires no particular equipment or exceptional skill. After a serious radiation accident, it can be easily performed in a short time in most medical facilities to obtain dose information to assist physicians.