DNA strand break induction, rejoining and cellular recovery in mammalian cells after heavy ion irradiation

Measurements on intracellular DNA strand break induction were performed using X-rays and various heavy charged particles. The alkaline unwinding technique and the alkaline and neutral filter elution techniques were applied. No variations in strand break induction were found between the different cell lines under investigation. For a given particle, both the LET and the particle energy determined the efficiency to induce DNA lesions. RBE values for the total amount of induced strand breaks were always smaller than 1. For DNA double strand breaks, RBE values only slightly larger than 1 were determined for particle radiation with an LET around 300 keV/#mu#m. Intracellular DSB/SSB ratios were found to be equivalent to data reported for in vitro systems using radioprotective conditions. Strand break rejoining as indicator of cellular repair processes was detected even after high-LET irradiation (LET #<=# 10000 keV/#mu#m). However, both the half times of rejoining and the fraction of residual DNA breaks increased with the atomic number of the particle. After particle irradiation with LET values beyond 10000 keV/#mu#m, no rejoining of DNA strand breaks was found. (orig.)SIGLEAvailable from TIB Hannover: RO 801(93-14) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman