Since the beneficial effects induced by low-dose radiation (0.01～0.5 Gy) was usually
certified in normal cells, we compared the induction of adaptive responses of different
properties of the cells: normal mouse lymphocytes (NL); L929 cells established from
mouse connective tissue; primary mouse keratinocytes (PK); v-rasHa trasnformed mouse
keratinocytes (ras-PK); line 308 from mouse papilloma; EL-4 cells from mouse lymphoma,
radiation-sensitive lymphoma cells, L5178Y-S; radiation-resistant lymphoma
cells, L5178Y-R. The time interval for the induction of the adaptive response was 4 hrs
and 7 hrs. The adaptive response was observed in NL, PK, L929, and L5178Y-R, but
not in L5178Y-S, EL-4, ras-PK, and 308 as determined by cell survival. Apoptosis was
also reduced by priming the exposure of low-dose radiation in NL, PK, L929, and
L5178Y-R cells, when detected using DNA ladder or TUNEL assay. These results
suggest that adaptive response by low dose preirradiation is induced in normal or primed
cells and apoptosis pathway is involved in these adaptive responses.

Keywords: Adaptive response, Gamma-ray, Low dose, Apoptosis, Normal cells,
Neoplastic cells