[Structural rearrangements of the chromatin during the adaptive response in two genetically close djungarian hamster fibroblast cell lines with different radiosensitivity].

The capacity of cell for the adaptive response (AR) induction after gamma-irradiation using micronuclear test was investigated. Our model consists of the parental djungarian hamster embryonic fibroblast cell line DH-TK- and its radioresistant progeny (PIC-20). We demonstrated that AR for the more radiosensitive parental cell line was shifted to the lower adaptive and to the challenge doses. The maximal AR for DH-TK- cells was induced at 0.3 Gy adaptive dose and 1.5 Gy challenge dose (adaptive response coefficient (ARC) was 0.4+/- 0.1), whereas for PIC-20 cells these means were 0.5 Gy and 3.0 Gy correspondingly (ARC = 0.45+/-0.1). Using the method of anomalous viscosity time dependence (AVTD) we demonstrated the chromatin rearrangements in both cell lines during 3-5 h after adaptive dose application. The rearrangement degree evaluated by the relative maximal reduced viscosity was considerably higher in PIC-20 cell line than that in DH-TK cells (2.4+/-0.3 vs 1.4+/-0. 1). Interestingly, the time of chromatin rearrangement did not depend neither on the dose nor on the cell type and was similar in both cell lines after 5 h of adaptive dose application. It was also shown that during the AR chromatin relaxation was lower after exposure to both the adaptive and challenge doses than after challenge dose only. In contrast, in the degree of AR chromatin relaxation was higher for both cell lines.