[Spermatogenesis in dogs during chronic gamma irradiation over years and in the aftereffect period].

Morphological parameters of spermatogenesis of 60 test and 12 control dogs exposed to a 6-year irradiation with total doses of 21 to 1140 rad were studied. The capacity for reparative regeneration of testes was maintained during the 5-6 years of irradiation at a dose rate of 0.06 and 0.17 rad/day. Early signs of radiation injury of testes were clearly observed during the first years of irradiation at a dose rate of 125 rad/year and progressively developed with an increase in the total dose. Inhibition of spermatogenesis reached maximum (atrophy of the spermatogenic epithelium, depletion of canaliculi) by the end of the first year of combined irradiation (190 rad/year). Spermatogenesis returned to normal in the animals that received a total dose of 570 rad during a 3-year irradiation exposure and were sacrificed 4.5 years after the onset of the experiment.