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Comparative biochemical study on glucocorticoid metabolism in mammary gland and kidney

乳腺和肾脏糖皮质激素代谢的比较生化研究

基本信息

批准号：
07806037
负责人：
MORI Makoto
金额：
$ 1.28万
依托单位：
Shizuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Corticosteroid action is modulated by the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD) Two isozymes of 11 beta-HSD are now recognized : 11 beta-HSD-1 is NADP-dependent enzyme with a Km in the micromolar range. 11 beta-HSD-2 is NAD-dependent enzyme with a Km in the nanomolar range. In the liver, 11 beta-HSD-1 is predominant and converts 11-dehydrocorticosterone to corticosterone. On the other hand, in the kidney, the NAD-dependent 11 beta-HSD-2 oxidatively inactivates corticosterone, allowing the nonselective mineralocorticoid receptor to be occupied by mineralocorticoids. The present study was conducted to show that 11 beta-HSD-2 is present in other sodium-transporting epithelia such as those in the mammary gland of mammals and in the reproductive tract of egg-laying birds.The microsome fraction was prepared from homogenates of kidney and various parts of oviduct of Japanese quail, and incubated with traitiated corticosterone for 1 hr at 40 C in the presence or absence of 1 mM NAD.The reaction was stopped, and the steroid was extracted by ethyl acetate. Separation of steroids was performed using a thin-layr chromatography developed in a chloroform-methanol (95 : 5) system. Activity of 11 beta-HSD-2 was determined by measuring the conversion rate of corticosterone to 11-dehydrocorticosterone.Among a number of tissues studied, the shell gland and albumen secreting region of the oviduct showed high activity of 11 beta-HSD-2. In these tissue, radioactive corticosterone was exclusively metabolized to 11-dehydrocorticosterone. On the other hands, infundibulum and isthmus of the oviduct and the vagina contain low activity, indicationg that these parts might not be a target of the mineralocorticoids. Although the process of secretion of albumen and the formation of egg shell is not known to be mediated by mineralocorticoids, our findings indicate that these tissues might be a target of the mineralocorticoids.

皮质类固醇的作用受11 β-羟基类固醇脱氢酶（11 β-HSD）的调节。11 β-HSD有两种同工酶：11 β-HSD-1是NADP依赖性酶，Km在微摩尔范围内。11 β-HSD-2是NAD依赖性酶，Km在纳摩尔范围内。在肝脏中，11 β-HSD-1占主导地位，并将11-脱氢皮质酮转化为皮质酮。另一方面，在肾脏中，NAD依赖性11 β-HSD-2氧化灭活皮质酮，使非选择性盐皮质激素受体被盐皮质激素占据。本研究表明，11 β-HSD-2存在于其他钠转运上皮细胞中，如哺乳动物的乳腺和产蛋鸟类的生殖道中的上皮细胞。微粒体部分是从日本鹌鹑的肾和输卵管的各个部分的匀浆中制备的，并在存在或不存在1 mMNAD的条件下，在40 ℃下与三氢化皮质酮孵育1小时。停止反应，用乙酸乙酯萃取类固醇。在氯仿-甲醇（95：5）体系中，用薄层色谱法分离甾体化合物。通过测量皮质酮向11-脱氢皮质酮的转化率来测定11 β-HSD-2的活性。在所研究的许多组织中，输卵管的壳腺和蛋白分泌区显示出高活性的11 β-HSD-2。在这些组织中，放射性皮质酮仅代谢为11-脱氢皮质酮。另一方面，输卵管和阴道的漏斗和峡部含有低活性，表明这些部位可能不是盐皮质激素的靶点。虽然蛋白的分泌和蛋壳的形成过程是不知道的盐皮质激素介导的，我们的研究结果表明，这些组织可能是盐皮质激素的目标。