DNA-DAMAGE INDUCTION BY I-125 ESTROGEN

DNA damage induced by the radioactive decay of I-125-estrogen (I-125-V ME2) in an estrogen receptor expressing CHO cell line, CHO-ER, was mea sured. I-125-VME2 targeted I-125 atoms proximal to DNA estrogen respon se elements (EREs). I-125 decays were accumulated at -135 degrees C, a nd thereafter assayed by alkaline and neutral filter elution technique s to measure DNA single strand break (ssb) and double strand break (ds b) induction respectively. Increasing DNA damage (both ssbs and dsbs) was detected after exposure of cells to increasing concentrations of I -125-VME2. DNA ssb and dsb dose-response curves for I-125-VME2 were mu ltiphasic. The rates of DNA damage induction by the decay of I-125-VME 2 was determined by comparing slopes of all data or by comparing initi al slopes. DNA ssb induction per I-125-VME2 decay was approximately 2 times greater compared with DNA dsb induction. I-125-VME2 decay induce d approximately 4-8 times more DNA dsbs than (125)IUdR decay.