Shan L X, Bardin C W, Hardy M P
Center for Biomedical Research, Population Council, New York, New York 10021, USA.
Endocrinology. 1997 Mar;138(3):1259-66. doi: 10.1210/endo.138.3.4973.
Leydig and Sertoli cells are both targets of androgen action in the testis. Androgen exerts contrasting effects on the two cell types partially inhibiting steroidogenesis in adult Leydig cell and stimulating adult Sertoli cell functions required to support spermatogenesis. The developmental changes in the messenger RNA (mRNA) levels of androgen receptor (AR) also differ between Leydig and Sertoli cells, with Leydig cell AR mRNA being highest on day 35 postpartum, whereas Sertoli cell AR mRNA levels are highest on day 90. The purpose of the present study was to determine if the concentrations of AR in Leydig and Sertoli cells are differentially regulated during development using quantitative immunostaining. AR protein levels were measured in rat testes after hormonal treatments at three developmental stages: on days 21, 35, and 90 postpartum. At each age, five groups of animals were treated for 4 days with: 1) vehicle; 2) LHRH antagonist (NalGlu, 0.3 mg/kg BW.day) to suppress endogenous levels of androgen that accompany inhibition of LH and FSH secretion; 3) NalGlu + LH (0.2 mg/kg BW.day); 4) NalGlu + testosterone (T, at 7.5 mg/kg BW.day); and 5) NalGlu + MENT (a potent synthetic androgen, 7 alpha-methyl-19-nortestosterone, 0.7 mg/kg BW.day). AR protein was visualized by immunohistochemistry and measured by computer-assisted image analysis in Leydig and Sertoli cells using frozen sections of tests. After NalGlu treatment, AR levels in Leydig cells declined sharply to 42% and 31% of vehicle control (P < 0.01) in the 21 and 35 days postpartum age groups, respectively, but in 90-day-old rats there was no change. AR levels were partially maintained by exogenous LH, and completely maintained by exogenous androgen treatments in Leydig cells from 21- and 35-day-old rats, whereas in Leydig cells from 90-day-old rats, AR levels were unaffected in all treatment groups. In contrast, after NalGlu treatment, the AR concentration in Sertoli cells from 90-day-old rats were reduced to 32% of control (P < 0.01). Moreover, in Sertoli cells from 90-day-old rats, AR levels were partially maintained by LH and completely maintained by androgens. A similar trend was observed on day 35. On day 21, however, AR levels in immature Sertoli cells were unaffected in all treatment groups. These results indicate that androgen maximally stimulates AR levels in immature Leydig cells but is without significant effect in adult Leydig cells. In contrast, AR levels in Sertoli cells are more sensitive to androgen regulation in adult compared with immature animals. These findings indicate that there are distinct mechanisms controlling AR concentrations in Leydig and Sertoli cells during the development of the testis.
睾丸间质细胞和支持细胞都是睾丸中雄激素作用的靶细胞。雄激素对这两种细胞类型产生相反的作用，部分抑制成年间质细胞的类固醇生成，并刺激支持精子发生所需的成年支持细胞功能。雄激素受体（AR）信使核糖核酸（mRNA）水平的发育变化在间质细胞和支持细胞之间也有所不同，间质细胞AR mRNA在产后第35天最高，而支持细胞AR mRNA水平在第90天最高。本研究的目的是使用定量免疫染色来确定在发育过程中间质细胞和支持细胞中AR的浓度是否受到不同的调节。在三个发育阶段进行激素处理后，测量大鼠睾丸中的AR蛋白水平：产后第21天、第35天和第90天。在每个年龄组，将五组动物用以下药物处理4天：1）赋形剂；2）促性腺激素释放激素拮抗剂（NalGlu，0.3mg/kg体重·天）以抑制伴随促黄体生成素（LH）和促卵泡生成素（FSH）分泌抑制的内源性雄激素水平；3）NalGlu + LH（0.2mg/kg体重·天）；4）NalGlu + 睾酮（T，7.5mg/kg体重·天）；5）NalGlu + MENT（一种强效合成雄激素，7α-甲基-19-去甲睾酮，0.7mg/kg体重·天）。使用睾丸冰冻切片，通过免疫组织化学使AR蛋白可视化，并通过计算机辅助图像分析在间质细胞和支持细胞中进行测量。NalGlu处理后，产后21天和35天年龄组的间质细胞中AR水平分别急剧下降至赋形剂对照的42%和31%（P < 0.01），但在90日龄大鼠中没有变化。在21日龄和35日龄大鼠的间质细胞中，外源性LH部分维持AR水平，外源性雄激素处理完全维持AR水平，而在90日龄大鼠的间质细胞中，所有处理组的AR水平均未受影响。相比之下，NalGlu处理后，90日龄大鼠支持细胞中的AR浓度降至对照的32%（P < 0.01）。此外，在90日龄大鼠的支持细胞中，AR水平由LH部分维持，由雄激素完全维持。在第35天观察到类似趋势。然而，在第21天，所有处理组中未成熟支持细胞的AR水平均未受影响。这些结果表明，雄激素最大程度地刺激未成熟间质细胞中的AR水平，但对成年间质细胞没有显著影响。相比之下，与未成熟动物相比，成年支持细胞中的AR水平对雄激素调节更敏感。这些发现表明，在睾丸发育过程中，存在控制间质细胞和支持细胞中AR浓度的不同机制。
