Role of spermatogonia in the repair of the seminiferous epithelium following x-irradiation of the rat testis.

Abstract

AbstractIn the normal adult rat testis, type A0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A1 spermatogonia.The behavior of type A0 and A1 spermatogonia was investigated following administration of a single dose of x‐rays (300 r) to the testis. Using whole mounts of seminiferous tubules, the type A0 and A1 cells were counted at various intervals after irradiation. At 8 and 13 days after irradiation, type A1 spermatogonia reached lowest values, i.e., 6% and 3% of non‐irradiated control, while type A0 reached the lowest value, i.e., 62% of control at eight days. Thereafter the numbers of type A0 and A1 progressively increased to return to normal at 39 days. It was thus concluded that the type A0 were comparatively more resistant to x‐irradiation than type A1 spermatogonia.To verify if the surviving type A0 proliferated in the irradiated testis, animals were injected with 3H‐thymidine three hours before they were sacrificed at various times after x‐irradiation. In irradiated testes the labeling indices of the surviving type A (A0, A1–A4) were the same as in the non‐irradiated testes except in stages V‐VI of the cycle of the seminiferous epithelium. While in the controls only 2% of type A cells were labeled at these two stages of the cycle, after irradiation the labeling index of type A reached a maximum of 31% at 13 days to return to control values by 39 days. Since at 13 days after irradiation type A0 spermatogonia were the predominant component of the spermatogonial population, it was concluded that these cells must have incorporated 3H‐thymidine and thereby contributed to the reconstruction of the spermatogonial population partially destroyed by irradiation.