Abstract
We measured the growth rates of various primary human fibroblasts under very low levels of high LET particles. This was performed using an incubator and a radiation detector located in the HIMAC biology beam room. NHEJ deficient 180BR cells (Ligase IV mutant) showed an immediate growth delay after about 10mGy accumulated exposure (6days) while there is no clear delay in normal as well as ataxia telangiectasia (AT) cells for more than 50 days. 180 BR cells in the HIMAC incubator also showed an accelerated senescence. These phenomena indicate the involvement of NHEJ proteins in the cell growth control. In order to access damage caused by low level high LET radiation, we have compared cell growth between cells exposed to 0.1Gy carbon particles (LET=80keV/um) and cells exposed to 0.1Gy X-rays. A significant growth delay was observed in normal cells irradiated with carbon ions for the first 5 days while much less delay was seen in cells with X-rays,suggesting that the damage by high LET is severer than by X-rays. [J Radiat Res 44:394 (2003)]
