Effect of epidermal growth factor (EGF) and insulin on the kinetics of radiation-induced DNA lesions repair.

To study the effect of both epidermal growth factor and insulin in terms of possible regulation of the repair process in cells, the time-course dependence of SSB and DSB repair have been investigated either in the presence of EGF (10 micrograms/ml) and insulin (1 microgram/ml) or without these factors in the medium (either supplemented with 10% serum or without serum) on Swiss 3T6 cells, exposed to ionizing radiation at a dose of 5-10 Gy using methods of neutral and alkaline elution as well as centrifugation on alkaline sucrose gradients. The absence of serum in the incubation medium during 18 to 24 hours before irradiation resulted in a sharp decrease in the rate of the repair of both single-strand break (SSB) and double-strand break (DSB). When cells were exposed to EGF and insulin immediately before irradiation the processes were restored to a significant extent. Data suggest that in the absence of other serum components, EGF and with insulin, are involved in the regulation of the repair of radiation-induced DNA lesions.