Santulli R, Sprando R L, Awoniyi C A, Ewing L L, Zirkin B R
Department of Population Dynamics, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
Endocrinology. 1990 Jan;126(1):95-101. doi: 10.1210/endo-126-1-95.
In a previous study it was demonstrated that spermatogenesis can be maintained quantitatively with exogenously administered testosterone in adult intact rats that lack LH. The studies described herein were designed to examine the extent to which spermatogenesis can be maintained quantitatively with exogenously administered testosterone in adult rats that lack all pituitary hormones. Adult male rats were hypophysectomized and testosterone was administered at the time of hypophysectomy via sustained release polydimethylsiloxane (PDS) capsules of increasing lengths. We used the PDS capsules to clamp testosterone at defined concentrations within the seminiferous tubule fluid over a 2- to 3-month treatment period. Mean testis weights and advanced spermatid numbers per testis stabilized by 8 weeks of testosterone treatment regardless of testosterone dose. Both testis weight and advanced spermatid number responded to testosterone dose, reaching plateaus of 1.2 g and 170 x 10(6) per testis, respectively. These values were 60% of, and significantly less than, the respective control values. This result was in striking contrast to the results of our previous study of LH-suppressed intact rats, in which exogenously administered testosterone resulted in testis weights and advanced spermatid numbers that plateaued at values not significantly different from those in controls. These different effects of testosterone in intact and hypophysectomized rats occurred despite the fact that the seminiferous tubule fluid testosterone concentrations achieved in the hypophysectomized rats (up to 25 ng/ml) were greater than the minimal testosterone concentration found previously to be required to maintain spermatogenesis quantitatively in LH-suppressed intact rats (13 ng/ml). Taken together, these results demonstrate clearly that intratesticular testosterone doses that are as high as or higher than those that maintain spermatogenesis quantitatively in intact rats lacking LH fail to maintain spermatogenesis quantitatively in rats lacking all pituitary hormones.
在先前的一项研究中已证明，在缺乏促黄体生成素（LH）的成年未阉割大鼠中，外源性给予睾酮可定量维持精子发生。本文所述的研究旨在探讨在缺乏所有垂体激素的成年大鼠中，外源性给予睾酮能在多大程度上定量维持精子发生。成年雄性大鼠接受垂体切除手术，并在垂体切除时通过不同长度的缓释聚二甲基硅氧烷（PDS）胶囊给予睾酮。在2至3个月的治疗期内，我们使用PDS胶囊将睾酮浓度维持在生精小管液中的特定水平。无论睾酮剂量如何，睾酮治疗8周后，平均睾丸重量和每个睾丸中的晚期精子细胞数量均趋于稳定。睾丸重量和晚期精子细胞数量均对睾酮剂量有反应，分别达到每个睾丸1.2克和170×10⁶的平台期。这些值分别为相应对照值的60%，且显著低于对照值。这一结果与我们先前对LH抑制的未阉割大鼠的研究结果形成了鲜明对比，在先前的研究中，外源性给予睾酮导致睾丸重量和晚期精子细胞数量达到的平台期值与对照组无显著差异。尽管垂体切除大鼠中生精小管液睾酮浓度（高达25纳克/毫升）高于先前发现的在LH抑制的未阉割大鼠中定量维持精子发生所需的最低睾酮浓度（13纳克/毫升），但睾酮在未阉割和垂体切除大鼠中仍产生了不同的作用。综上所述，这些结果清楚地表明，在缺乏LH的未阉割大鼠中能定量维持精子发生的睾丸内睾酮剂量，在缺乏所有垂体激素的大鼠中却无法定量维持精子发生。
