Poletti A, Coscarella A, Negri-Cesi P, Colciago A, Celotti F, Martini L
Istituto di Endocrinologia, Università di Milano, Italy.
Steroids. 1998 May-Jun;63(5-6):246-51. doi: 10.1016/s0039-128x(98)00018-x.
The enzyme 5 alpha-reductase (5 alpha-R) activates several delta 4-3keto steroids to more potent derivatives which may also acquire new biological actions. Testosterone gives rise to the most potent natural androgen dihydrotestosterone (DHT), and progesterone to dihydroprogesterone (DHP), a precursor of the endogenous anxiolytic/anesthetic steroid tetrahydroprogesterone (THP). Two isoforms of 5 alpha-R, with a limited degree of homology, different biochemical properties and distinct tissue distribution have been cloned: 5 alpha-R type 1 and type 2. In androgen-dependent structures DHT is almost exclusively formed by 5 alpha-R type 2; 5 alpha-R type 1 is widely distributed in the body, with the highest levels in the liver, and may be involved in steroid catabolism. In the brain, the roles of the two isozymes are still largely unknown. This brief review will summarize recent experimental data from our laboratory which try to assign possible functional roles to the process of 5 alpha-reduction, and to the two 5 alpha-R isoforms in the CNS.
5α-还原酶（5α-R）可将多种δ4-3-酮类固醇激活为活性更强的衍生物，这些衍生物可能还会获得新的生物学活性。睾酮可转化为活性最强的天然雄激素双氢睾酮（DHT），孕酮则转化为双氢孕酮（DHP），后者是内源性抗焦虑/麻醉类固醇四氢孕酮（THP）的前体。现已克隆出5α-R的两种亚型，它们的同源性有限，生化特性不同，组织分布也各异：5α-R1型和5α-R2型。在雄激素依赖性结构中，DHT几乎完全由5α-R2型生成；5α-R1型在体内广泛分布，在肝脏中含量最高，可能参与类固醇的分解代谢。在大脑中，这两种同工酶的作用仍 largely未知。本简要综述将总结我们实验室最近的实验数据，这些数据试图为5α-还原过程以及中枢神经系统中两种5α-R亚型赋予可能的功能作用。
