Simple biodosimetry method for use in cases of high-dose radiation exposure that scores the chromosome number of Giemsa-stained drug-induced prematurely condensed chromosomes (PCC).

There is a need for quick dose estimation by a simple method in radiation accidents. This study develops a simple and rapid dose estimation protocol for victims of such accidents, in particular those involving high radiation doses. Human peripheral blood lymphocytes (PBL) were gamma-irradiated in vitro at several dose points up to 60 Gy, and were stimulated with phytohaemagglutinin-P (PHA-P) for 2 days to obtain dividing cells. PBL were then forced to condense prematurely, using 50 nM calyculin A, and the obtained chromosome spreads were Giemsa stained. The G2-PCC (prematurely condensed chromosomes) index and chromosome number for each radiation dose point were scored. G2-PCC were stably induced using calyculin A within 24 h delays in stimulation of PBL with PHA-P. The chromosome number of G2-PCC increased steeply with radiation doses up to 30 Gy at a rate of 0.31 Gy(-1) and then decreased at 0.30 Gy(-1) up to 40 Gy. More than 10% of G2-PCC index remained up to a 15 Gy dose. Even after 40 Gy irradiation, about 2% PCC index was obtained, and this value was enough to score a sufficient number of chromosome spreads for analysis. Therefore, the combined use of chromosome number and G2-PCC index allows biodosimetry to be done easily and rapidly. If PCC are not induced using calyculin A, it is strongly suggested that the radiation dose is over 50 Gy. A rapid and easy dose estimation for large dose exposure whole-body was realized by combined analysis of Giemsa-stained chromosome number of G2-PCC and PCC index using calyculin A. This simple method will be of use for rapid decision making of therapy for radiation accident victims. This method also has potential for use as a biodosimeter for partial-body exposure accidents.