THE EFFECTS OF 2560 r OF X-RAYS ON SPERMATOGENESIS IN THE MOUSE

Abstract

1. Changes in the cellular composition of the seminiferous tubules induced by exposure to 2560 r of x-rays have been analyzed by a quantitative histological procedure. These data have been compared with the results obtained following exposure to a much lower dose (320 r) in an attempt to gain further insight with respect to the manner in which the observed changes are brought about.2. Ėxposure to 320 r results in a temporary maturation depletion of the seminiferous epithelium. This is brought about mainly by the inhibition of spermatogonial mitosis with irradiation-induced spermatogonial necrosis playing only a minor role. In contrast, exposure to 2560 r produces a permanent depletion due to the fact that surviving spermatogonia are incapable of sustained regenerative efforts.3. The frequency of necrotic spermatogonia, following 2560 r, was found to be double the peak value attained in the 320 r material, or four times that of the corresponding controls.4. Taken together, the data for the 320 r and 2560 r experiments suggest that spermatogonial depletion is brought about in two ways: (1) by suppression of mitosis due to inhibition of DNA synthesis, and (2) the killing of cells. Irradiation-induced necrosis plays a much more important role following exposure to high doses of x-rays. Even so the frequency of necrosis in either experiment did not reach very high levels, being about 9% after the low dose and about 15% in the case of the high x-ray dose.5. Further evidence was obtained in support of the view that relatively heavily damaged cells may undergo degenerative changes prior to the onset of division, while less heavily damaged cells manifest degenerative changes only at about the time of entry into mitosis.