Mutation induction in V79 Chinese hamster cells by very heavy ions

Mutation induction (resistance to 6-thioguanine) in Chinese hamster fibroblasts (V79) by exposure to accelerated heavy ions (O, Ne, Ca, Ti, Ni, Xe, Pb and U with energies between 5 and 14.8 MeV/u) was investigated, covering a range of LET from 300 to about 15,700 KeV/micron. The LET-dependence of the mutation induction cross-section (sigma m) has, in a similar way to inactivation (sigma i), to be described by separate curves for each ion. Both sigma m and mutagenicity (sigma m/sigma i) decrease with increasing specific energy for any given ion. Relative biological effectiveness for mutation induction was found to be significantly smaller than unity for the ions and energies investigated.