Koshida H, Miyamori I, Ikeda M, Saito Z, Takeda R
Second Department of Internal Medicine, School of Medicine, Kanazawa University, Japan.
Nihon Naibunpi Gakkai Zasshi. 1988 Nov 20;64(11):1199-208. doi: 10.1507/endocrine1927.64.11_1199.
Several aldosterone metabolites are now known to possess some mineralocorticoid activities. In order to test the hypothesis that these metabolites could contribute to the pathogenesis of hypertension, we studied the aldosterone metabolism in SHR in vitro and in vivo. In vitro experiment, male SHR and WKY rats of 4 and 15 weeks of age were used. The microsome, cytosol and heavy mitochondria fractions from liver and kidney were isolated by ultracentrifuge. 10mg protein/ml of each subcellular fraction was incubated with 3H-aldosterone in Tris-HCl buffer at pH 7.4 containing NADPH, glucose-6-phosphate (G-6-P) and G-6-P dehydrogenase as described by Morris, D.J. et al. (Hypertension, 5 (suppl. I]: I-35-I-40, 1983.). Aldosterone and its metabolites synthesized were extracted with Sep-pak C18 cartridges and separated by HPLC on a reverse phase column. In vivo experiments, the urine of male SHR and WKY rats of 15 weeks old injected 10 microCi 3H-aldosterone intraperitoneally was collected for 48 hours, extracted and analyzed by HPLC. Peaks of steroids from SHR were compared with those from WKY. Incubation of aldosterone with liver microsomes yielded at least 10 polar and 3 less polar metabolites (A-ring reduced metabolites). SHR liver microsomes synthesized larger amounts of 3 polar metabolites than WKY liver microsomes. Liver cytosol, liver heavy mitochondria and kidney subcellular fractions mainly synthesized less polar metabolites, but failed to synthesize as much polar metabolites as liver microsomes. Kidney microsomes and cytosol from 4 weeks old SHR synthesized larger amounts of less polar metabolites compared to those from WKY. In vivo experiment, SHR of 15 weeks of age excreted larger amounts of 2 polar metabolites than WKY. The present study suggests that the difference of metabolism of aldosterone between SHR and WKY observed from an early stage in the liver and the target organ, kidney, may be associated with hypertension or its causative factors, and confirms that aldosterone will be metabolized to several polar and less polar forms by rat liver and kidney subcellular fractions.
现已发现几种醛固酮代谢产物具有一定的盐皮质激素活性。为了验证这些代谢产物可能参与高血压发病机制的假说，我们在体外和体内研究了自发性高血压大鼠（SHR）的醛固酮代谢情况。在体外实验中，使用了4周龄和15周龄的雄性SHR和Wistar Kyoto大鼠（WKY）。通过超速离心法分离肝脏和肾脏的微粒体、胞质溶胶和重线粒体部分。按照Morris, D.J.等人（《高血压》，5[增刊I]：I-35-I-40，1983年）所述，将各亚细胞部分10mg蛋白质/ml与3H-醛固酮在含有NADPH、葡萄糖-6-磷酸（G-6-P）和G-6-P脱氢酶的pH 7.4 Tris-HCl缓冲液中孵育。合成的醛固酮及其代谢产物用Sep-pak C18柱提取并用反相柱通过高效液相色谱法分离。在体内实验中，收集腹腔注射10微居里3H-醛固酮的15周龄雄性SHR和WKY大鼠48小时的尿液，进行提取并用高效液相色谱法分析。将SHR的类固醇峰与WKY的进行比较。醛固酮与肝脏微粒体孵育产生至少10种极性代谢产物和3种极性较小的代谢产物（A环还原代谢产物）。SHR肝脏微粒体合成的3种极性代谢产物比WKY肝脏微粒体多。肝脏胞质溶胶、肝脏重线粒体和肾脏亚细胞部分主要合成极性较小的代谢产物，但未能合成与肝脏微粒体一样多的极性代谢产物。4周龄SHR的肾脏微粒体和胞质溶胶合成的极性较小的代谢产物比WKY的多。在体内实验中，15周龄的SHR排泄的2种极性代谢产物比WKY多。本研究表明，在肝脏和靶器官肾脏中从早期就观察到的SHR和WKY之间醛固酮代谢的差异可能与高血压或其致病因素有关，并证实醛固酮将被大鼠肝脏和肾脏亚细胞部分代谢为几种极性和极性较小的形式。
