Span P N, Sweep C G, Benraad T J, Smals A
Department of Medicine, University Hospital Nitjmegen, The Netherlands.
Eur J Endocrinol. 1996 Mar;134(3):386-92. doi: 10.1530/eje.0.1340386.
The rat prostate, a classical androgen-target tissue, contains both known isozymes of steroid 5alpha-reductase. i.e. type I and type II. So far, the role of the type I isozyme has been proposed as catabolic. The abundant expression of type I 5alpha-reductase in an androgen-target tissue is therefore puzzling. Assessment of the subcellular localization of 5alpha-reductase isozymes in rat prostate might contribute in elucidating their possibly distinct roles. After obtaining crude subcellular fractions by differential centrifugation, both isozyme activities were measured at neutral pH by plotting according to Eadie-Scatchard. The observations were extended by assessment of pH-dependent velocity ratios and type II 5alpha-reductase inhibitor sensitivities in these subcellular fractions. The results indicated a preferentially--although not exclusively--nuclear localization for the type I and a predominantly microsomal localization for the type II isozyme activity in the rat prostate. In conclusion, the nuclear localization of the type I isozyme seems not to concur with its proposed catabolic role.
大鼠前列腺作为一种典型的雄激素靶组织，含有类固醇5α-还原酶的两种已知同工酶，即I型和II型。到目前为止，I型同工酶的作用被认为是分解代谢的。因此，I型5α-还原酶在雄激素靶组织中的大量表达令人费解。评估大鼠前列腺中5α-还原酶同工酶的亚细胞定位可能有助于阐明它们可能不同的作用。通过差速离心获得粗亚细胞组分后，根据伊迪-斯卡查德（Eadie-Scatchard）作图法在中性pH下测量两种同工酶的活性。通过评估这些亚细胞组分中pH依赖性速度比和II型5α-还原酶抑制剂敏感性，扩展了观察结果。结果表明，在大鼠前列腺中，I型同工酶优先定位于细胞核（尽管并非唯一），II型同工酶活性主要定位于微粒体。总之，I型同工酶的核定位似乎与其所提出的分解代谢作用不一致。
