Number of Spermatogonia after X-irradiation of the Adult Rat

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Abstract
The testes of adult rats were exposed to 0-3000 r X-irradiation, and the animals were killed 6 hours to 21 days after treatment. The numbers of type-A, intermediate, and type-B spermatogonia, degenerating cells and mitotic figures were counted in fifty cross sections of seminiferous tubules in each testis. Statistical analyses showed that a curvilinear relationship exists between the number of type-A spermatogonia, and the number of intermediate and type-B spermatogonia, and (a) the dose administered and (b) the time after irradiation. The survival curves for type-A spermatogonia are indicative of a population of cells possessing a heterogeneity of radio-sensitivities. A comparison of the present results with corresponding data reported for the mouse by Oakberg reveals that for a given dose, the rate of depletion and subsequent recovery of spermatogonia is slower, and the incidence of degenerating cells lower, in the rat than in the mouse. The results suggest that the depletion of spermatogonia in the rat may be due primarily to an inhibition of mitosis of some type-A spermatogonia rather than to cell-death.