Mammalian spermatogenesis as a biological dosimeter for ionizing radiation

Mammalian spermatogenesis is an extremely sensitive in vivo system for biologic dosimetry of ionizing radiation. Differentiated spermatogonia which are responsible for the radiation-induced reduction of DNA-synthesizing testicular cells are the most sensitive cells we know in adult mammals. The D50-dose of murine S-phase diminution is about 0.25 Gy. The dose-response relationship of S-phase reduction with 200 kV X-rays is shown in the range from 2.5 Gy down to 0.1 Gy using data from flow cytophotometric analysis of ethidium bromide/mithramycin stained cells. In addition to the inactivation of spermatogonia the value of mutagenic actions of ionizing radiation on spermatogenic cells (the increase of the coefficient of variation and of the frequency of diploid spermatids) for biologic dosimetry is investigated. These data are compared with other models of bilogic dosimetry using spermatogenic cells. The application of this system to man is discussed as well. (orig.)