Comparative Effects of Negative Pions, Neutrons, and Photons on Testes Weight Loss and Spermatogenic Stem-Cell Survival in Mice

A comparison of the relative biological potency of fast neutrons, negative pions, and photons was made with decrease in testes weight and spermatogenic cell survival as endpoints. The predominant effect on these endpoints of the different LET radiations was a change in the slopes of the dose-response curves. Since the relative changes in slopes to different LET radiations were approximately the same for each endpoint, both endpoints yielded similar estimates of relative biological potency. The relative biological potency of neutrons, peak pions, and plateau pions relative to¹³⁷ Cs γ rays or 300-kVp X rays for producing testicular damage were, respectively, 2.8, 1.5, and 1.2.