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.

皮质类固醇作用由 11 β-羟基类固醇脱氢酶 (11 β-HSD) 调节。现已认识到 11 β-HSD 的两种同工酶： 11 β-HSD-1 是 NADP 依赖性酶，Km 在微摩尔范围内。 11 beta-HSD-2 是 NAD 依赖性酶，Km 在纳摩尔范围内。在肝脏中，11β-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 11β-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。本研究的目的是表明 11β-HSD-2 存在于其他钠转运上皮细胞中，例如哺乳动物的乳腺和产蛋鸟类的生殖道中。微粒体部分是从以下物质的匀浆中制备的：取日本鹌鹑的肾脏和输卵管各部分，在存在或不存在 1 mM NAD 的情况下，与特征化皮质酮在 40°C 孵育 1 小时。用乙酸乙酯萃取类固醇。使用在氯仿-甲醇（95:5）系统中开发的薄层色谱法进行类固醇的分离。通过测量皮质酮向11-脱氢皮质酮的转化率来测定11β-HSD-2的活性。在研究的许多组织中，输卵管的壳腺和蛋白分泌区显示出11β-HSD-2的高活性。在这些组织中，放射性皮质酮完全代谢为 11-脱氢皮质酮。另一方面，输卵管漏斗部和峡部以及阴道的活性较低，表明这些部分可能不是盐皮质激素的目标。尽管尚不清楚蛋白分泌和蛋壳形成的过程是由盐皮质激素介导的，但我们的研究结果表明这些组织可能是盐皮质激素的靶标。