Mineralocorticoid versus glucocorticoid receptor occupancy mediating aldosterone-stimulated sodium transport in a novel renal cell line
Mineralocorticoid versus glucocorticoid receptor occupancy mediating aldosterone-stimulated sodium transport in a novel renal cell line
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DOI：
10.1681/asn.2004121110
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发表时间：
2005-04-01
影响因子：
13.6
通讯作者：
Rossier, BC
中科院分区：
文献类型：
--
作者：
Gaeggeler, HP;Gonzalez-Rodriguez, E;Rossier, BC
醛固酮通过调节上皮钠通道（ENaC）介导的钠沿醛固酮敏感的远端肾元转运来控制钠平衡，远端肾元表达矿皮质激素（MR）和糖皮质激素受体（GR）。矿化皮质激素的特异性是由2型11 β -羟基类固醇脱氢酶保证的，该酶将皮质醇或皮质酮代谢为不能结合MR和/或GR的无活性代谢物。醛固酮介导醛固酮敏感的远端肾元中钠转运反应对MR和GR的部分占用尚不能在体内研究。为了回答这个问题，研究人员使用了一种新的小鼠皮质收集管细胞系（mCCD(cl1)），该细胞系表达了显著水平的MR和GR以及强大的醛固酮钠转运反应。醛固酮引起双相反应：低剂量（K-1/2 =约0.5 nM）引起钠转运的短暂和早期增加（在3小时达到峰值），而高剂量（K-1/2 =约90 nM）引起大约三倍大的持久反应。在3小时时，皮质酮的闭合响应曲线比醛固酮的曲线右移了两个log以上的浓度，在11 β -羟基类固醇脱氢酶2型抑制剂卡贝诺洛酮的存在下，这种效应完全恢复。低剂量地塞米松（0.1 ~ 1 nM）未能诱导早期反应，但高剂量引起持久反应（K-1/2约8 nM），与高浓度醛固酮相似。平衡结合试验表明，醛固酮和皮质酮都结合到一个高亲和力、低容量的位点，而地塞米松只结合一个位点。在醛固酮浓度的生理范围内，预计钠转运在生理周期内由MR占用控制，在盐限制或急性应激期间由MR和GR占用控制。
Aldosterone controls sodium balance by regulating an epithelial sodium channel (ENaC)-mediated sodium transport along the aldosterone-sensitive distal nephron, which expresses both mineralocorticoid (MR) and glucocorticoid receptors (GR). Mineralocorticoid specificity is ensured by 11 beta-hydroxysteroid dehydrogenase type 2, which metabolizes cortisol or corticosterone into inactive metabolites that are unable to bind MR and/or GR. The fractional occupancy of MR and GR by aldosterone mediating the sodium transport response in the aldosterone-sensitive distal nephron cannot be studied in vivo. For answering this question, a novel mouse cortical collecting duct cell line (mCCD(cl1)), which expresses significant levels of MR and GR and a robust aldosterone sodium transport response, was used. Aldosterone elicited a biphasic response: Low doses (K-1/2 = approximately 0.5 nM) induced a transient and early increase of sodium transport (peaking at 3 h), whereas high doses (K-1/2 = approximately 90 nM) entailed an approximately threefold larger, long-lasting response. At 3 h, the corticosterone close-response curve was shifted to the right compared with that of aldosterone by more than two log concentrations, an effect that was fully reverted in the presence of the 11 beta-hydroxysteroid dehydrogenase type 2 inhibitor carbenoxolone. Low doses of dexamethasone (0.1 to 1 nM) failed to induce an early response, but high doses elicited a long-lasting response (K-1/2 approximately 8 nM), similar to that observed for high aldosterone concentrations. Equilibrium binding assays showed that both aldosterone and corticosterone bind to a high-affinity, low-capacity site, whereas dexamethasone binds to one site. Within the physiologic range of aldosterone concentrations, sodium transport is predicted to be controlled by MR occupancy during circadian cycles and by MR and GR occupancy during salt restriction or acute stress.