Grino P B, Griffin J E, Wilson J D
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8857.
Endocrinology. 1990 Feb;126(2):1165-72. doi: 10.1210/endo-126-2-1165.
Testosterone and dihydrotestosterone are believed to exert their androgenic effects by interacting with a single intracellular receptor protein in androgen target tissues. During fetal life, however, testosterone mediates the virilization of the Wolffian ducts into the epididymis, vas deferens, and seminal vesicles, whereas the urogenital sinus and external genitalia require the in situ conversion of testosterone to dihydrotestosterone to undergo male development. The reason why the signal provided by testosterone needs to be amplified in some androgen target tissues but not in others remains an enigma. To provide insight into the different actions of these androgens we studied their interaction with the human androgen receptor in fibroblasts cultured from the genital skin of a patient with 5 alpha-reductase deficiency. Dihydrotestosterone was formed in negligible amounts in these cells, and in some experiments the residual 5 alpha-reductase activity was further blocked with the 5 alpha-reductase inhibitor finasteride. Saturation analysis in fibroblast monolayers disclosed similar amounts of binding with testosterone and dihydrotestosterone, and the affinity of binding of dihydrotestosterone was, on the average, about 2-fold greater than that of testosterone. [3H]Testosterone also exhibited a 5-fold faster dissociation rate from the receptor than [3H]dihydrotestosterone. In thermolability experiments the [3H]testosterone-receptor complex displayed marked instability at 42 C with 2 nM [3H] testosterone, whereas with 20 nM [3H]testosterone, receptor stability was similar to that seen with [3H]dihydrotestosterone. In up-regulation experiments, 2 nM [3H]testosterone produced a 34% increase in specific androgen receptor binding after 24 h, whereas 20 nM [3H]testosterone produced an average increase of 64%. Our results suggest that the weaker androgenic potency of testosterone compared to that of dihydrotestosterone resides in its weaker interaction with the androgen receptor, most clearly demonstrable as an increase in the dissociation rate of testosterone from the receptor. When present in relatively high concentrations, however, testosterone overcomes this defect by mass action.(ABSTRACT TRUNCATED AT 400 WORDS)
睾酮和双氢睾酮被认为是通过与雄激素靶组织中的单一细胞内受体蛋白相互作用来发挥其雄激素作用的。然而，在胎儿期，睾酮介导中肾管发育为附睾、输精管和精囊，而泌尿生殖窦和外生殖器则需要睾酮在原位转化为双氢睾酮才能进行男性发育。为什么睾酮提供的信号在某些雄激素靶组织中需要放大而在其他组织中不需要，这仍然是一个谜。为了深入了解这些雄激素的不同作用，我们研究了它们与一名5α-还原酶缺乏症患者生殖器皮肤培养的成纤维细胞中的人雄激素受体的相互作用。在这些细胞中双氢睾酮的生成量可忽略不计，并且在一些实验中，用5α-还原酶抑制剂非那雄胺进一步阻断了残余的5α-还原酶活性。成纤维细胞单层的饱和分析显示，睾酮和双氢睾酮的结合量相似，并且双氢睾酮的平均结合亲和力比睾酮大约高2倍。[3H]睾酮从受体上解离的速率也比[3H]双氢睾酮快5倍。在热稳定性实验中，2 nM [3H]睾酮存在时，[3H]睾酮-受体复合物在42℃时表现出明显的不稳定性，而当[3H]睾酮浓度为20 nM时，受体稳定性与[3H]双氢睾酮相似。在上调实验中，2 nM [3H]睾酮在24小时后使特异性雄激素受体结合增加了34%，而20 nM [3H]睾酮平均增加了64%。我们的结果表明，与双氢睾酮相比，睾酮较弱的雄激素效力在于其与雄激素受体的相互作用较弱，最明显的表现为睾酮从受体上解离速率的增加。然而，当睾酮以相对较高的浓度存在时，它通过质量作用克服了这一缺陷。（摘要截短至400字）
