Liang T, Heiss C E
J Biol Chem. 1981 Aug 10;256(15):7998-8005.
17 beta-N,N-Diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one (DMAA) is a potent reversible inhibitor of 5 alpha-reductase. The inhibition by DMAA of the conversion of testosterone to 5 alpha-dihydrotestosterone by rat prostate 5 alpha-reductase is competitive with testosterone, the apparent Ki being 5 nM, and uncompetitive with NADPH, DMAA inhibited both membrane-bound and solubilized 5 alpha-reductase. DMAA has moderate affinity for the prostate cytosol androgen receptor: 3 X 10(-6) M gives 50% inhibition of the binding of 10(-9) M 5 alpha-[3H]dihydrotestosterone to this receptor. This affinity to the androgen receptor is 1,000-, 500-, 120-, and 40-fold lower than that of 5 alpha-dihydrotestosterone, testosterone, spironolactone, and cyproterone acetate, respectively, and 7-fold higher than that of cimetidine. After incubation of [3H]testosterone with minced prostate, more than 90% of the radioactivity extracted from the nuclei co-chromatographed with 5 alpha-dihydrotestosterone and the rest with testosterone. DMAA at low concentrations decreased the ratio of 5 alpha-dihydrotestosterone to testosterone in the nuclei without significantly reducing the total uptake. DMAA at high concentrations also reduced the total radioactivity in the nuclei. This differential effect may reflect a higher affinity of DMAA for 5 alpha-reductase than for the androgen receptor. When 5 alpha-[3H]dihydrotestosterone was used in the tissue incubations, all radioactivity extracted from nuclei co-chromatographed with 5 alpha-dihydrotestosterone, regardless of whether or not DMAA was present. This nuclear uptake of 5 alpha-dihydrotestosterone is inhibited only by high concentrations of DMAA. In a cell-free system, the nuclear uptake of 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor was not inhibited by DMAA. These results suggest that DMAA may inhibit nuclear uptake of 5 alpha-dihydrotestosterone by inhibiting the receptor binding. Sucrose gradient centrifugation of the radioactive KCl nuclear extracts prepared from the tissue incubations showed that the nuclear [3H]testosterone-receptor complex has a greater rate of dissociation than does the nuclear 5 alpha-[3H]dihydrotestosterone-receptor complex. [3H]Testosterone prebound to the prostate cytosol receptor also dissociates faster than 5 alpha-[3H]dihydrotestosterone prebound to the cytosol receptor.
17β - N，N - 二乙基氨基甲酰基 - 4 - 甲基 - 4 - 氮杂 - 5α - 雄甾烷 - 3 - 酮（DMAA）是一种强效的5α - 还原酶可逆抑制剂。DMAA对大鼠前列腺5α - 还原酶将睾酮转化为5α - 二氢睾酮的抑制作用与睾酮呈竞争性，表观Ki为5 nM，与NADPH呈非竞争性。DMAA抑制膜结合型和可溶性5α - 还原酶。DMAA对前列腺胞质雄激素受体具有中等亲和力：3×10⁻⁶ M可使10⁻⁹ M 5α - [³H]二氢睾酮与该受体的结合受到50%的抑制。这种对雄激素受体的亲和力分别比5α - 二氢睾酮、睾酮、螺内酯和醋酸环丙孕酮低1000倍、500倍、120倍和40倍，比西咪替丁高7倍。用[³H]睾酮与切碎的前列腺一起孵育后，从细胞核中提取的放射性物质中，超过90%与5α - 二氢睾酮共色谱，其余与睾酮共色谱。低浓度的DMAA降低了细胞核中5α - 二氢睾酮与睾酮的比例，而不会显著降低总摄取量。高浓度的DMAA也降低了细胞核中的总放射性。这种差异效应可能反映了DMAA对5α - 还原酶的亲和力比对雄激素受体的亲和力更高。当在组织孵育中使用5α - [³H]二氢睾酮时，无论是否存在DMAA，从细胞核中提取的所有放射性物质都与5α - 二氢睾酮共色谱。5α - 二氢睾酮的这种核摄取仅被高浓度的DMAA抑制。在无细胞系统中，预先与胞质受体结合的5α - [³H]二氢睾酮的核摄取不受DMAA抑制。这些结果表明，DMAA可能通过抑制受体结合来抑制5α - 二氢睾酮的核摄取。对从组织孵育制备的放射性KCl核提取物进行蔗糖梯度离心显示，细胞核[³H]睾酮 - 受体复合物的解离速率比细胞核5α - [³H]二氢睾酮 - 受体复合物的解离速率更高。预先与前列腺胞质受体结合的[³H]睾酮的解离速度也比预先与胞质受体结合的5α - [³H]二氢睾酮的解离速度更快。
