Ion content and the response of L5178Y-R and L5178Y-S cells to X rays and ionophore A23187.

We examined the response of L5178Y-S (radiosensitive, LY-S) and L5178Y-R (radioresistant, LY-R) lymphoblasts to X-irradiation with concomittant treatment with divalent cation ionophore, A23187 (3 h or 5 h, 5 micrograms/ml). Cells treated with A23187 alone progressed through the cell cycle more slowly than the untreated cells and their cloning efficiency was reduced. In both cell strains the ionophore prolonged duration of the postirradiation mitotic delay. Radiation-induced inhibition of DNA synthesis was reversed by A23187 in LY-S but not in LY-R cells. Cells subjected to the ionophore treatment survived X-irradiation in almost the same way as untreated cells, as if the effect of A23187 treatment were reversed by irradiation. There was also a reversion in the ion content: A23187 caused a marked increase in Na+ content and a decrease in K+ content, irradiation itself did not change the ion content, whereas in the A23187-treated cells it restored almost the same pattern as that found in the control cells. We found less Mg2+ ions in LY-S cells after treatment with A23187 and A23187 + X than in LY-R cells, in relation to untreated (control) cells. These observations point to the possible importance of ion transport for recovery from radiation damage.