Zhu L J, Hardy M P, Inigo I V, Huhtaniemi I, Bardin C W, Moo-Young A J
The Population Council, Center for Biomedical Research, New York, New York 10021, USA.
Biol Reprod. 2000 Aug;63(2):368-76. doi: 10.1095/biolreprod63.2.368.
Androgen is essential for maintenance of spermatogenesis in the testis and for maturation of spermatozoa in the epididymis. The effects of androgen are mediated through its receptor (AR), the levels of which are, in turn, regulated by androgen. Previous studies have shown that AR concentrations in Leydig and Sertoli cells are differentially regulated during development. The aim of the present study was to determine if cell-type-specific regulation of AR by androgen occurs in testicular and epididymal cells during adulthood. Adult male rats were treated with the LHRH-antagonist Azaline B (100 g/day) by osmotic pump for 1, 2, 3, 4, or 8 wk to suppress endogenous androgen, with identical numbers of intact control animals at each time period. An androgen replacement group was simultaneously treated with the antagonist and a synthetic androgen, 7 alpha-methyl-19-nortestosterone (MENT), during the final 4 wk of the experiment. Levels of nuclear AR protein in specific cell types were quantified by immunohistochemistry in conjunction with computer-assisted image analysis. Levels of AR in testicular cells declined sharply after treatment with the LHRH antagonist. In Sertoli cells, nuclear AR levels decreased to 8% of control (P < 0. 01) after 4 wk treatment; and to 12% and 17% of control (P < 0.01) in Leydig and myoid cells, respectively. Androgen replacement resulted in complete recovery of nuclear AR levels in Sertoli cells (93%, P > 0.05) but in only partial recovery in myoid (69%, P < 0. 01) and Leydig cells (56%, P < 0.01). In the epididymis, tubular epithelial cells and stromal cells differed in their responses to the LHRH antagonist. After 1 wk, nuclear AR levels in caput stromal cells decreased dramatically to 34% of control (P < 0.01) and in cauda stromal cells to 43% (P < 0.01). In contrast, the decline of AR levels in epididymal epithelial cells was not as dramatic as that in stromal cells. After 1 wk, the decline in the caput and cauda was to 87% and 76% of control, respectively. After 8 wk, nuclear AR levels in stromal cells further declined to 1.1% in caput and 1.4% in cauda, whereas in the epithelial cells, a smaller decline in nuclear AR was noted (to 30% in the caput and 45% in the cauda). After androgen replacement with MENT, nuclear AR levels recovered to more than 90% of control in both epididymal cell types. These results indicate that AR levels in the nuclei of adult Sertoli cells depend mainly on the level of androgen, whereas in the adult Leydig and myoid cells, the androgen dependency is more limited. The results also indicate that in the epididymis, stromal cells are more sensitive than epithelial cells to the regulation of AR levels by androgen.
雄激素对于维持睾丸中的精子发生以及附睾中精子的成熟至关重要。雄激素的作用是通过其受体（AR）介导的，而AR的水平又反过来受雄激素调控。先前的研究表明，在发育过程中，睾丸间质细胞和支持细胞中AR的浓度受到不同的调节。本研究的目的是确定成年期睾丸和附睾细胞中雄激素对AR是否存在细胞类型特异性调节。成年雄性大鼠通过渗透泵接受促性腺激素释放激素（LHRH）拮抗剂阿扎林B（100μg/天）处理1、2、3、4或8周以抑制内源性雄激素，每个时间段设置相同数量的完整对照动物。在实验的最后4周，雄激素替代组同时接受拮抗剂和合成雄激素7α-甲基-19-去甲睾酮（MENT）处理。通过免疫组织化学结合计算机辅助图像分析对特定细胞类型中的核AR蛋白水平进行定量。用LHRH拮抗剂处理后，睾丸细胞中的AR水平急剧下降。在支持细胞中，处理4周后核AR水平降至对照的8%（P<0.01）；在睾丸间质细胞和类肌细胞中分别降至对照的12%和17%（P<0.01）。雄激素替代导致支持细胞中核AR水平完全恢复（93%，P>0.05），但类肌细胞（69%，P<0.01）和睾丸间质细胞（56%，P<0.01）仅部分恢复。在附睾中，管腔上皮细胞和基质细胞对LHRH拮抗剂的反应不同。1周后，头段基质细胞核AR水平急剧降至对照的34%（P<0.01），尾段基质细胞降至43%（P<0.01）。相比之下，附睾上皮细胞中AR水平的下降不如基质细胞明显。1周后，头段和尾段分别降至对照的87%和76%。8周后，基质细胞核AR水平在头段进一步降至1.1%，在尾段降至1.4%，而在上皮细胞中，核AR下降幅度较小（头段降至30%，尾段降至45%）。用MENT进行雄激素替代后，两种附睾细胞类型中的核AR水平均恢复至对照的90%以上。这些结果表明，成年支持细胞中的核AR水平主要取决于雄激素水平，而在成年睾丸间质细胞和类肌细胞中，雄激素依赖性较为有限。结果还表明，在附睾中，基质细胞比上皮细胞对雄激素调节AR水平更为敏感。
