Changes in sensitivity of cells during exposure to radiation at low dose-rate.

Abstract

SummaryA large sparing effect was observed for Chlamydomonas reinhardii when dose-rate was reduced. Cells given radiation at low dose-rate were subsequently given series of graded doses at a high dose-rate. Values of D0 were larger, and extrapolation numbers lower for survival curves at high dose-rate, following low dose-rate pre-treatment, than if no pre-treatment had been given. The processes which led to a change in sensitivity of cells, and lower extrapolation numbers for survival curves at high dose-rate following low dose-rate pre-treatment, may have contributed to the overall sparing effect of a reduction in dose-rate. Because the shape of the split-dose survival curve at high dose-rate was different from that of the single-dose survival curve, current models, which relate changes in shapes of survival curves as dose-rate is reduced to recovery of cells from sublethal damage, could not be applied.