Comparative study of G2 delay and survival after241Americium-? and60Cobalt-? irradiation

Abstract

Survival and G2 delay following exposure to either⁶⁰Cobalt-γ-rays or²⁴¹Americium-α-paticles were studied in eight mammalian cell lines of human and animal origin including human fibroblasts from normal individuals and from patients with Ataxia telangiectasia or Fanconi's anemia. For both endpoints the effectiveness of alpha particles was greater as compared toγ-rays. RBE values for G2 delay (4.6–9.2) were in general comparable to RBE values derived from initial slopes of survival curves (RBE _α ) but higher compared to the ratio of mean inactivation doses $\left( {RB_{\bar DML} } \right)$ . Ataxia cells were particularly sensitive to cell killing byγ-irradiation (D₃₇ = 0.57 Gy), however, showed average sensitivity toα-particles of high LET (D₃₇ = 0.30 Gy). With the exception of Ataxia cells, cell killing and G2 delay seem to be related processes if individual cell cycle parameters are taken into account.