Bartlett J M, Spiteri-Grech J, Nieschlag E
Max Planck Clinical Research Unit for Reproductive Medicine, Münster, Federal Republic of Germany.
Endocrinology. 1990 Aug;127(2):747-58. doi: 10.1210/endo-127-2-747.
Stage synchronization of seminiferous epithelium after withdrawal and replenishment of vitamin A provides a valuable and powerful approach to the investigation of paracrine interactions within the testis. However, since the discovery of this model, little attention has been given to the events surrounding the synchronous reinitiation of spermatogenesis after depletion of vitamin A. Synchronization of spermatogenesis was observed in all animals previously deficient in vitamin A. However, the degree of synchrony observed, as assessed by a ratio of synchrony, decreased markedly with time. The possibility that spermatogenic synchrony decreases with time due to variability of the temporal duration of stages of the cycle of the seminiferous epithelium is supported by this observation. However, long-term studies are required to substantiate this point. After initiation of stage synchrony of spermatogenesis, increased testicular concentrations of epidermal growth factor (EGF) were observed in testes synchronized between stages IX-II than at other stages of the cycle of the seminiferous epithelium. This elevation in testicular EGF concentrations correlated well with mitotic division of type A spermatogonia at stages IX, XII, and XIV of the cycle of the seminiferous epithelium. Previous in vitro studies have implicated an EGF-like factor in the stimulation of type A spermatogonial division in the mouse. A significant increase in testicular insulin-like growth factor I (IGF-I) concentrations was observed in control animals 14 days after the injection of retinol acetate. In vitamin A deficient animals, a marked increase in testicular IGF-I concentrations was observed as compared to age-matched controls. Maximal levels of testicular IGF-I concentrations were present 14 and 28 days and again 126 days after re-supplementation with retinol acetate. No stage dependent changes in testicular IGF-I were observed but the data provided suggest the retinol may be one of the factors involved in the regulation of testicular IGF-I.
维生素A撤除与补充后生精上皮的阶段同步化，为研究睾丸内旁分泌相互作用提供了一种有价值且强大的方法。然而，自该模型被发现以来，对于维生素A耗竭后精子发生同步重新启动周围的事件关注甚少。在所有先前缺乏维生素A的动物中均观察到精子发生的同步化。然而，通过同步率评估观察到的同步程度随时间显著下降。这一观察结果支持了生精同步性随时间下降可能是由于生精上皮周期各阶段时间持续的变异性这一可能性。然而，需要长期研究来证实这一点。在精子发生阶段同步化启动后，在IX-II期之间同步的睾丸中观察到表皮生长因子（EGF）的睾丸浓度升高，高于生精上皮周期的其他阶段。睾丸EGF浓度的这种升高与生精上皮周期IX、XII和XIV期A型精原细胞的有丝分裂密切相关。先前的体外研究表明，一种EGF样因子参与刺激小鼠A型精原细胞分裂。在注射醋酸视黄醇14天后，对照动物的睾丸胰岛素样生长因子I（IGF-I）浓度显著增加。与年龄匹配的对照相比，在维生素A缺乏的动物中，观察到睾丸IGF-I浓度显著增加。在重新补充醋酸视黄醇后14天和28天以及再次在126天时，睾丸IGF-I浓度达到最高水平。未观察到睾丸IGF-I的阶段依赖性变化，但所提供的数据表明视黄醇可能是参与睾丸IGF-I调节的因素之一。
