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.

现在认识到11个β-HSD的两个同工酶，通过酶11β-羟基甾体脱氢酶（11β-HSD）调节皮质类固醇的作用：11 beta-HSD-1是NADP依赖性酶，在微极范围内为km。 11β-HSD-2是NAD依赖性酶，在纳摩尔范围内具有km。在肝脏中，11个Beta-HSD-1主要是主导，将11-脱水的皮质酮转换为皮质酮。另一方面，在肾脏中，NAD依赖性的11β-HSD-2氧化失活可使皮质酮失活，从而使非选择性的盐皮质激素受体被矿物皮质激素占据。 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。反应停止，并用乙酸乙酯提取类固醇。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-脱水的可替胶酮的转化率来确定11β-HSD-2的活性。在研究的许多组织中，壳腺和蛋白分泌区域的分泌区域表现出高活性11β-HSD-2。在这些组织中，放射性皮质酮仅代谢为11-氢化霉酮。另一方面，输卵管和阴道的漏斗和地峡含有低活性，表明这些部分可能不是盐皮质激素的靶标。尽管蛋白的分泌过程和蛋壳的形成过程尚不为矿物皮质激素介导，但我们的发现表明这些组织可能是矿物皮质激素的靶标。