Abstract：
We have previously described local aldosterone synthesis in mouse colon. In the renin-angiotensin-aldosterone system (RAAS), angiotensin II (Ang II) peptide is the physiological factor which stimulates aldosterone synthesis in the adrenal glands. We have recently demonstrated that Ang II stimulates aldosterone synthesis also in mouse colon. Here, we conducted a 75-min ex vivo incubation of murine colonic tissue and evaluated the effects of three other Ang peptides, Ang I (1 μM), Ang III (0.1 μM) and Ang (1-7) (0.1 μM) on aldosterone synthesis. As a possible mechanism, their effects on tissue levels of the rate-limiting enzyme, aldosterone synthase (CYP11B2) were measured by ELISA and Western blot. Ang III significantly elevated the amount of tissue CYP11B2 protein in colon. The values of released aldosterone in colon tissue incubation were increased over the control in the presence of Ang I, II or III, however, being statistically non-significant. In Western blot analysis, the values of tissue CYP11B2 protein content were elevated by Ang I and II. Ang (1-7) alone in colon did not influence CYP11B2 protein levels in the incubation experiment but showed higher aldosterone release without statistical significance. Ang (1-7) showed an antagonistic effect towards Ang II in release of aldosterone in adrenal gland. An overall estimation of a single peptide (three measured variables), the results were always in an increasing direction. The responses of aldosterone synthesis to high levels of glucose (44 mM) and potassium (18.8 mM) as physiological stimulators in vivo were investigated in the colon incubation. Glucose, equal to four times the concentration of the control buffer in the incubation, showed higher values of aldosterone release in colon than control without statistical significance similarly to the effect seen in adrenal glands. Increasing the concentration of potassium in the incubation buffer exerted no effect on colonic aldosterone production. Intriguingly, no correlation was found between aldosterone release and the tissue CYP11B2 protein content in colon. In summary, the response of colonic aldosterone synthesis to different Ang peptides resembles, but is not identical to, the situation in the adrenal glands.
摘要：
我们先前已经描述了小鼠结肠中的局部醛固酮合成。在肾素-血管紧张素-醛固酮系统（RAAS）中，血管紧张素II（AngII）肽是刺激肾上腺醛固酮合成的生理因子。我们最近证明AngII也刺激小鼠结肠中的醛固酮合成。这里,我们对小鼠结肠组织进行了75分钟的离体孵育，并评估了其他三种Ang肽的作用，AngI(1μM),AngIII（0.1μM）和Ang（1-7）（0.1μM）对醛固酮合成的影响。作为一种可能的机制，它们对限速酶组织水平的影响，用ELISA和Westernblot检测醛固酮合成酶(CYP11B2)。AngIII显着升高结肠中组织CYP11B2蛋白的量。在存在AngI的情况下，结肠组织孵育中释放的醛固酮的值比对照增加，II或III，然而,在统计上不显著。在蛋白质印迹分析中，组织CYP11B2蛋白含量的值随AngI和AngII的升高而升高。在孵育实验中，单独的Ang（1-7）在结肠中不影响CYP11B2蛋白水平，但显示出更高的醛固酮释放，无统计学意义。Ang（1-7）在肾上腺释放醛固酮时对AngII具有拮抗作用。单个肽的总体估计（三个测量变量），结果总是朝着增加的方向发展。在结肠孵育中研究了醛固酮合成对高水平葡萄糖（44mM）和钾（18.8mM）作为体内生理刺激剂的反应。葡萄糖,等于孵育中对照缓冲液浓度的四倍，显示结肠中醛固酮释放的值高于对照组，没有统计学意义，与肾上腺中看到的效果相似。增加孵育缓冲液中钾的浓度对结肠醛固酮的产生没有影响。有趣的是，醛固酮释放与结肠组织CYP11B2蛋白含量无相关性。总之,结肠醛固酮合成对不同Ang肽的反应类似，但不等同于，肾上腺的情况。
