Chemically induced premature chromosome condensation in human fibroblast cell lines: fundamental study for applications to the biodosimetry of local exposure.

The premature chromosome condensation (PCC) of human peripheral lymphocytes treated with inhibitors of protein phosphatase has been demonstrated to be an excellent tool for the estimation of high-dose whole-body exposure. To develop a new biodosimetry for local exposure, the cytogenetical reaction of human fibroblast lines to PCC inducers was examined and compared with that of lymphocytes. The efficiency of the induction by calyculin A was greater than that by okadaic acid in both cell types. Calyculin A induced PCC in 5-Gy-irradiated and unirradiated samples at almost the same frequency in the lymphocytes, whereas the efficacy was considerably lower in irradiated fibroblasts than in unirradiated ones. Calcium ionophore enhanced the induction of PCC in irradiated fibroblasts, although PCC frequencies were still much lower than those in the lymphocytes. The frequency of ring chromosomes observed in 2- and 5-Gy-irradiated fibroblasts was too low to be used as a marker for cytogenetic dosimetry, and that of excess fragments, scored as the observed chromosome number minus 46, might be substituted. The frequency of excess fragments for 2-, 5-, and 10-Gy-irradiated fibroblasts was less than 0.75, about 1 and a few per cell, respectively, although these values changed with the culture period. The prospects and limitations of the application of PCC techniques to fibroblasts are discussed.