Stability of spermatogenic synchronization achieved by depletion and restoration of vitamin A in rats

Studies of synchronization of spermatogenesis following vitamin A deficiency have suggested that this may provide an in vivo model for the study of stage-dependent changes in hormonal action and protein secretion within the seminiferous epithelium. However, until now, no information on the stability or durability of this condition has been available. In this study, 200 seminiferous tubules from each of 40 rats (including controls) were classified according to their spermatogenic stage after withdrawal and replenishment of vitamin A. Following 15 wk withdrawal and subsequent replenishment of vitamin A, spermatogenesis was initiated in a synchronous fashion. This synchrony remained stable for more than 10 cycles of the seminiferous epithelium (2.5 spermatogenic cycles). In association with the extended period of vitamin A deficiency, a proportion of tubules (30%) showed morphological characteristics of either Sertoli cells only or Sertoli cells plus spermatogonia with occasional pachytene spermatocytes. During the 11-wk period of observation in this study, no significant change in proportions of damaged tubules were observed. Testicular testosterone concentrations, although elevated with respect to controls, showed no correlation with the stage of the cycle of the seminiferous epithelium observed, whereas pituitary and serum follicle-stimulating hormone levels were elevated, probably due to the number of damaged tubules observed. The persistence of synchrony in spermatogenesis following vitamin A treatment suggests that this model is applicable for studies of paracrine actions within the testis. However, the decreased ratio of synchrony observed with time may provide evidence that duration of the individual stages of the cycle of the seminiferous epithelium might be subject to temporal variation, leading to a progressive desynchronization of spermatogenesis in this model system.