Abstract
The time of transfer of a signal required for a bystander effect expressed in an adjacent cell of an X-irradiated cell via gap junction (GJ) has been estimated by using pulse-like treatment of lindane (γ-BHC), an inhibitor of the GJ function. X-ray microbeam with a diameter of 100 micrometer was available from a micro-capillary tube installed in a table-top X-ray fluorescence analyzer for local specimen area (XGT-2700, HORIBA Ltd.). Human neonatal dermal fibroblasts were used for their normal GJ function judged by the Lucifer yellow transfer method. First, the concentration and the treatment time of lindane were determined to exert a maximal inhibitory effect in a minimal treatment time. The treatment of 25 μM for 30 minutes was adopted for the cells used. The complete recovery from the inhibition by removing lindane was observed after 2 hrs. Therefore the GJ function can be inhibited for a period of about 2.5 hrs. Second, time dependence of the transfer of a bystander signal was estimated by changing the time of lindane administration after irradiation. The detection of a bystander effect was performed by p53 expression around an irradiated cell after 24 hrs. The bystander effect was detected at 1, 2 and 4 hrs after irradiation, while in the case of 3 hrs significant reduction of the p53 expression area was observed. These results suggest that the time of the transfer of a bystander signal for the p53 expression is around 4 hrs after irradiation.
