Zirkin B R, Santulli R, Awoniyi C A, Ewing L L
Department of Population Dynamics, Johns Hopkins University School of Hygiene and Public Health, Baltimore, Maryland 21205.
Endocrinology. 1989 Jun;124(6):3043-9. doi: 10.1210/endo-124-6-3043.
The studies described herein were designed to examine whether there is a threshold concentration of testosterone (T) within the seminiferous tubules that is required to maintain spermatogenesis in the rat, or alternatively, whether there is a dose-response relationship between the intratesticular T concentration and the maintenance of spermatogenesis. T was administered to intact adult male rats via sustained release polydimethylsiloxane capsules in order to experimentally clamp T at well defined concentrations within the seminiferous tubules. Implantation of T-filled capsules of increasing sizes resulted in linear increases in T concentrations in serum, interstitial fluid, and seminiferous tubule fluid (STF). We examined the effect of step decreases in intratesticular T concentration on the numbers of advanced spermatogenic cells maintained by the testis over a 2-month period. Quantitatively complete spermatogenesis was maintained despite an 80% reduction in the STF T concentration (to approximately 13 ng/ml) from control values. The ability of the testis to maintain complete spermatogenesis was extremely sensitive to further decreases in STF T concentration. Thus, reduction of the STF T concentration from approximately 13 to 9 ng/ml resulted in a reduction in the number of advanced spermatids that were maintained in the testis by approximately 100 x 10(6). Reduction of the STF T concentration to approximately 4 ng/ml resulted in a further reduction in the number of advanced spermatids per testis by 100 x 10(6). Taken together, these data support the contention that there is far more T present within the seminiferous tubules of intact rat testes than is required to maintain quantitatively normal spermatogenesis and reveal for the first time that there is a dose-response relationship between the STF T concentration and the quantitative maintenance of advanced spermatogenic cells in the rat testis.
本文所述的研究旨在探讨在大鼠的生精小管内是否存在维持精子发生所需的睾酮（T）阈值浓度，或者睾丸内T浓度与精子发生维持之间是否存在剂量反应关系。通过持续释放聚二甲基硅氧烷胶囊给完整的成年雄性大鼠施用T，以便在生精小管内将T实验性地钳制在明确界定的浓度。植入尺寸不断增大的含T胶囊导致血清、间质液和生精小管液（STF）中T浓度呈线性增加。我们研究了睾丸内T浓度逐步降低对睾丸在2个月期间维持的高级生精细胞数量的影响。尽管STF中T浓度较对照值降低了80%（降至约13 ng/ml），但仍维持了定量完整的精子发生。睾丸维持完整精子发生的能力对STF中T浓度的进一步降低极为敏感。因此，将STF中T浓度从约13 ng/ml降至9 ng/ml导致睾丸中维持的晚期精子细胞数量减少了约100×10⁶。将STF中T浓度降至约4 ng/ml导致每个睾丸中晚期精子细胞数量进一步减少100×10⁶。综上所述，这些数据支持这样的观点，即完整大鼠睾丸的生精小管内存在的T远超过维持定量正常精子发生所需的量，并首次揭示了STF中T浓度与大鼠睾丸中高级生精细胞的定量维持之间存在剂量反应关系。
