摘要
糖皮质激素经受体介导对间质细胞中睾酮合成行使直接的抑制作用。间质细胞中１１β－羟类固醇脱氢酶（１１β－ＨＳＤ）通过控制细胞内糖皮质激素浓度调节睾酮合成。至今，已鉴定了两种１１β－ＨＳＤ同工酶，Ⅰ型从肝脏中纯化，是以ＮＡＤＰ（Ｈ）为辅酶的氧化还原酶。从肾脏纯化的Ⅱ型，是依赖ＮＡＤ的氧化酶。有关间质细胞中１１β－ＨＳＤ的研究，尤其对其特性的研究尚不深入。本研究通过测定间质细胞中Ⅰ型１１β－ＨＳＤ抗原及其ｍＲＮＡ表达，观察间质细胞中该酶的优势辅酶，纯化的活间质细胞中１１β－ＨＳＤ催化反应类型及间质细胞１１β－ＨＳＤ对糖皮质激素调节的反应等几个方面来评价间质细胞中１１β－ＨＳＤ的特性。结果发现，间质细胞显示Ⅰ型１１β－ＨＳＤ抗原及其ｍＲＮＡ的表达（ＲＴ－ＰＣＲ产物，６９６ｂｐ），未见有Ⅱ型ｍＲＮＡ表达。间质细胞中该酶是以ＮＡＤＰ（Ｈ）为优势辅酶（Ｐ＜０．０５），以氧化反应为优势的氧化还原酶（Ｐ＜０．０５）。切除肾上腺后大鼠其纯化的活间质细胞及培养的间质细胞１１β－ＨＳＤ氧化酶活性受糖皮质激素调节（Ｐ＜０．０５）。本研究表明，大鼠间质细胞中１１β－ＨＳＤ是一个以催化氧化反应为优势，以ＮＡＤＰ（Ｈ）为辅酶的Ⅰ型同工酶，?
lucocorticoids exert a direct inhibition on testosterone production by Leydig cells through glucocorticoid receptors-mediated process. 11β-hydroxysteroid dehydrogenase (11β-HSD) of Leydig cells modulates steroidogenesis by controlling the intracellular concentration of glucocorticoid within the Leydig cells. Two isoforms of 11β-HSD have been identified. Type Ⅰ first purified from rat liver is a NADP(H)-dependent oxidoreductase. Type Ⅱ purified from kidney is a NAD-dependent oxidase. It is superficial of the study of 11β-HSD, especially of its properties. The aim of the present study was to assess the properties of 11β-HSD in Leydig cells by measuring the type Ⅰ antigen and its mRNA expression for type Ⅰ in Leydig cells, by observing cofactor preference of 11β-HSD in Leydig cells, to determine whether 11β-HSD in freshly isolated Leydig cells is primarily oxidative or reductive, and its reaction to glucocorticoids regulation. The present study indicated that 34KD type Ⅰ antigen and RT-PCR product (696bp) for type Ⅰ mRNA were seen in Leydig cell, while type Ⅱ mRNA was undetectable. It was found that 11β-HSD in freshly isolated Leydig cells is bidirectional, with oxidative activity predominating and NADP-dependent (P<0.05). Both oxidative activities of 11β-HSD in freshly isolated and cultured Ldydig cells from adrenalectomized rat (ADX) are regulated by glucocorticoid (P<0.05), indicating that the glucocorticoids are involved in maintaining the predominance of 11β-HSD oxidation. We proposed the 11β-HSD in rat Leydig cells is type Ⅰ isoform with oxidative activity predominating. Its function is involved in glucocorticoid oxidation in Leydig cells and the activity is regulated by glucocorticoids.
