Activity and expression of 5alpha-reductase in human sebaceous glands and apocrine glands

双氢睾酮是由靶组织中的睾酮通过5α-还原酶生成的，在雄激素的作用中起着关键作用。本研究的目的是确定人类皮脂腺和顶分泌腺中存在哪种类型的5α-还原酶(类型或类型2)同工酶。分离的大汗腺保存在-70℃下，大汗腺匀浆与50 nm或1 mM的~3H-睾酮和1 mM的NADPH孵育20分钟。得到了以下结果。(1)pH的影响：两种浓度的睾酮在pH值为6-7.5时酶活最好。有3例获得了类似的结果。(2)睾酮浓度与5α-还原酶活性的关系：睾酮浓度从2 nM变化到60 mM，表明存在单一的酶。根据Lineweaver-Burk图估算的米氏常数约为21微米。(3)类型1抑制剂MK386的作用：在睾酮浓度为50 nm时，加入25 nm的MK386，酶活性降低到近20%。(4)RT-PCR分析显示，在25个周期中检测到类型1的表达，而在35个周期中未检测到类型2的表达。因此，结合我们先前的研究表明，双氢睾酮在臭症的顶分泌腺细胞核中占主导地位，我们目前的数据清楚地表明，类型1同工酶与顶分泌腺中的雄激素作用类似于皮脂腺，而不像在前列腺中。

Dihydrotestosterone, which is formed from testosterone by 5alpha-reductase in the target tissue, plays a key role in the androgen action. The goals of this study were to identify which isozyme of 5alpha-reductase (typel or type2) is present in the human sebaceous glands and apocrine glands.Apocrine sweat glands were dissected under a microscope from skin samples obtained by suction at surgical treatment of osmidrosis. Isolated apocrine glands were stored at-70 C.Homogenates of apocrine glands were incubated with 50nM or 1muM of ^3H-testosterone and 1mM of NADPH for 20 min. The following results were obtained. (1) Effect of pH : Optimal activity was observed at pH6-7.5 at both concentrations of testosterone. Similar results were obtained in three cases. (2) Relation between testosterone concentraion and 5alpha-reductase activity : Testosterone concentrations were changed from 2nM to 60muM.The results suggested the presence of a single enzyme. The Michaelis constant was about 21muM as estimated from Lineweaver-Burk plots. (3) Effexts of type1 inhibitor, MK386 : The enzyme activity was decreased to nearly 20% by the addition of 25nM of MK386 at the testosterone concentration of 50nM.(4) RT-PCR analysis revealed that type1 mRNA expression was detected at 25 cycles, whereas type2 mRNA was not detected even at 35 cycles.Thus, together with our previous study which showed the predominance of dihydrotestosterone in the nuclei of the apocrine gland of osmidrosis, our present data clearly demonstrate that type1 isozyme is responsible for the androgen action in the apocrine gland like in the sebaceous gland, but not like in the prostate.