Abstract
Purpose; In order to know the mechanisms of bystander effects through the secreted factor from irradiated cells, we examined the involvement of radicals induced by the conditioned medium from the irradiated cells.
Method; Bystander effects were detected by medium transfer method. The induction of mutations at HPRT locus by bystander effects was examined in CHO cells. Suppressive effects of bystander effects by ascorbic acid were analyzed by the treatments of recipient bystander cells. The radicals induced by conditioned medium in bystander cells were determined by ESR method.
Results; Bystander effects induced mutations at HPRT locus. In the analysis with ascorbic acid, it was effective for the suppression of bystander responses when recipient bystander cells were treated. Slow releasing long-lived radicals (SRLLR) were identified by ESR method in the cells treated with conditioned medium from irradiated cells, and ascorbic acid could relieve the induction of SRLLR, suggesting that the different types of radicals from reactive oxygen species (ROS) are involved in the bystander mutagenesis. These results suggest that inductions of SRLLR play an important role for the bystander mutagenesis in the recipient cells of secreted factors from irradiated cells.
