The Influence of Mutation Induction in Normal Human Fibroblasts Irradiated with X Rays and Iron Ions

Abstract

We investigated the influence of mutation induction on the hypoxanthine guanine phosphoribosyltransferase (hprt) locus in normal human fibroblasts irradiated with X rays or accelerated iron ions with LET ranging from 200 to 400 keV/μm. The relative biological effectiveness (RBE) of the mutation frequency per total number of surviving cells for iron ions with comparatively lower LET values (200 and 260 keV/μm) in this study was higher than 1, and the RBE for the 300 keV/μm, 350 keV/μm and 400 keV/μm ions was nearly 1. These results indicated that the mutation induction for iron ions decreased with increasing LET, and these of high-LET regions (over 300 keV/μm) and X rays were similar. The deletion spectrum of exons in hprt locus for X rays and 260 keV/μm-iron ions were analyzed using multiplex polymerase chain reaction (PCR). About 70% of mutant induced by iron ions showed deletion of the entire exons (total deletion), while mutant induced by X rays showed partial deletion, which one or more exons are missing, of about 70%. The results indicated that iron-ion induced mutants sustained severer damage than X-ray induced mutants even if the dose-response curves for mutation induction were similar between X rays and iron ions.