ROLE OF SPERMATOGONIA IN THE STAGE-SYNCHRONIZATION OF THE SEMINIFEROUS EPITHELIUM IN VITAMIN-A-DEFICIENT RATS

After 20‐day‐old rats are placed on a vitamin‐A‐deficient diet (VAD) for a period of 10 weeks, the seminiferous tubules are found to contain only Sertoli cells and a small number of spermatogonia and spermatocytes. Retinol administration of VAD rats reinitiates spermatogenesis, but a stage‐synchronization of the seminiferous epithelium throughout the testis of these rats is observed. In order to determine which cell type is responsible for this synchronization, the germ cell population has been analyzed in whole mounts of seminiferous tubules dissected from the testes of rats submitted to the following treatments. Twenty‐day‐old rats received a VAD diet for 10 weeks and then were divided into three groups of six rats. In group 1, all animals were sacrificed immediately; in group 2, the rats were injected once with retinol and sacrificed 3 hr later; in group 3, the rats were injected once with retinol, placed on a retinol‐containing diet for 7 days and 3 hr, and then sacrificed. Three rats from each group had one testis injected with 3H‐thymidine 3 hr (groups 1 and 2) or 7 days and 3 hr (group 3) before sacrifice. Three normal adult rats (approximately 100 days old) served as controls. Labeled and unlabeled germinal cells were mapped and scored in isolated seminiferous tubules. In group 1, type A1 and type A0 spermatogonia as well as some preleptotene spermatocytes were present; type A2 A3 A4 In, and B spermatogonia were completely eliminated from the testis. Neither type A1 mitotic figures nor 3H‐thymidine‐labeled‐type A1 nuclei were seen. Three hr after retinol injection (group 2), type A1 mitoses, but no labeled type A1 nuclei were observed. At 7 days and 3 hr after retinol administration (group 3), type A4 and In Spermatogonia as well as type A1 spermatogonia were present. A few residual pachytene spermatocytes were found, and some type A0 cells were labeled. These results indicate that VAD caused, in addition to an impairment of spermatogenesis at the preleptotene spermatocyte step, a selective momentary arrest of surviving type A1 spermatogonia at the G2 phase of their cell cycle. Following administration of vitamin A to VAD rats, these type A1 cells reinitiated spermatogenesis synchronously and, after several cycless of proliferation and renewai, reconstituted the seminiferous epithelium in a stage‐synchronized manner. Copyright © 1990 Wiley‐Liss, Inc.