Magnesium handling by the distal nephron

远端肾单位对镁的处理

基本信息

批准号：
10583069
负责人：
JAMES A MCCORMICK
金额：
$ 33.21万
依托单位：
OREGON HEALTH & SCIENCE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2023
资助国家：
美国
起止时间：
2023-01-20 至 2026-12-31
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10583069
关键词：
Acute Affect Amiloride Apical Atrophic Automobile Driving Cell physiology Chronic Cisplatin Clinical Coupled Data Dietary Magnesium Dietary Potassium Disease Disinhibition Distal Distal convoluted renal tubule structure Diuretics Electrolytes Etiology Excretory function Experimental Models Functional disorder Gene Expression Genetic Genetic Diseases Gitelman syndrome Homeostasis Human Hypertension Hypokalemia Hypomagnesemia KCNJ1 gene Kidney Knockout Mice Knowledge Life Limb structure Link Magnesium Magnesium Deficiency Measures Membrane Potentials Mg supplementation Missense Mutation Movement Mus Mutation Na(+)-K(+)-Exchanging ATPase Nephrons Normal Range Nutrient Optics Pathway interactions Pharmaceutical Preparations Phenotype Physiological Plasma Play Potassium Potassium Channel Process Recycling Refractory Renal clearance function Renal tubule structure Rest Role SLC12A3 gene Serum Site Structure Supplementation Syndrome Testing Thiazide Diuretics Thick Three-Dimensional Imaging Time Tissues absorption apical membrane chemotherapy cofactor epithelial Na+ channel hyperkalemia mouse model non-genetic novel pharmacologic preservation response symporter thiazide urinary wasting

项目摘要

Project summary Magnesium (Mg 2+ ) is an essential cofactor in many cellular processes, and disruption of Mg 2+ homeostasis can be life-threatening. Serum Mg 2+ is maintained within a narrow normal range by regulated reabsorption in the kidney. Mg The distal 2+ channel TRPM6/7, but reabsorption convoluted tubule (DCT) reabsorbs only a small fraction of the filtered Mg via the is tightly regulated in this segment. Most genetic causes of 2+ (10%) hypomagnesemia affecting DCT Mg2+ reabsorption. In (NCC) remain from diuretics. Mg NCC species that secretion, Familial changes the DCT, Na + reabsorption via the NaCl cotransporter plays a critical role in transcellular Mg + reabsorption, but the mechanisms linking the two processes unclear. Hypomagnesemia is observed in Gitelman and EAST syndromes, both of which ultimately arise loss of NCC activity, and following pharmacological NCC blockade with t he commonly used thiazide Chronically, DCT atrophy is observed with loss of NCC activity, and the resulting l oss of capacity for 2+ eabsorption s believed to be the major mechanism of renal Mg 2+ wasting. However, the early effects of inhibition on renal Mg 2+ handling are less clear. Our preliminary data in mice support findings in other that thiazides transiently lower, rather than increase, urinary Mg 2+ excretion. Based on this we propose reduced Mg 2+ excretion occurs following an acute K + load, which inhibits NCC to promote downstream K + serving to preserve serum Mg 2+ . In contrast, renal Mg 2+ handling appears norma in the disease Hyperkalemic Hypertension (FHHt), in which NCC is hyperactivated. Aim 1 will test the hypothesis that in DCT 2 r i l Na+ reabsorption modify Mg2+ handling prior to DCT remodeling, and this is physiologically relevant. We will use inducible mouse models of Gitelman syndrome, EAST syndrome, thiazide administration, and K+ loading to test this. We will perform time-course analyses and measure changes in electrolyte handling, and in DCT structure with optical tissue clearing and 3-D imaging. Hypomagnesemia and hypokalemia are commonly seen together clinically e.g. following cisplatin chemotherapy. Hypokalemia is often refractory to K+ supplementation unless hypomagnesemia is resolved, but the underlying mechanisms have not been determined. Aim 2 will test two proposed mechanisms that promote K+ secretion along the connecting segment and are supported by our preliminary data: (i) Mg2+-dependent disinhibition of the K+ channel ROMK and (ii) increased Na+ delivery from DCT. We will determine NCC, ENaC, and ROMK activities in hypomagnesemic mice and a new mouse model of hypomagnesemia/hypokalemia by performing diuretic response tests. We will also test whether Mg2+ supplementation can mitigate K+ losses in mouse models with inducible NCC inhibition. The apical K+ channel Kv1.1 has been proposed to generate the membrane potential that provides the drive for Mg2+ entry along the DCT, since human Kv1.1 mutations cause hypomagnesemia. However, experimental evidence is lacking. To test this, In Aim 3 we will phenotype a novel renal tubule-specific Kv1.1 knockout mouse, and determine whether Kv1.1 determines the apical membrane potential in the early DCT.

项目概要镁（镁 2+ ) 是许多细胞过程中重要的辅助因子，并且会破坏 Mg 2+ 体内平衡可以会危及生命。血清镁 2+ 通过调节重吸收将其维持在狭窄的正常范围内肾。镁远端 2+通道TRPM6/7，但重吸收回旋小管 (DCT) 仅重吸收过滤后的镁的一小部分该领域受到严格监管。大多数遗传原因 2+ (10%) 低镁血症影响 DCT Mg2+ 重吸收。在 (NCC) 保持从利尿剂。镁 NCC 物种那分泌，家族式变化 DCT、Na + 通过 NaCl 协同转运蛋白重吸收在跨细胞 Mg + 重吸收中起关键作用，但连接这两个过程的机制不清楚。在 Gitelman 和 EAST 综合征中观察到低镁血症，这两种综合征最终都会出现 NCC 活性丧失，以及用常用的噻嗪类药物阻断 NCC 后长期来看，DCT 萎缩伴随着 NCC 活性的丧失，以及由此导致的能力丧失。 2+ 吸收被认为是肾脏 Mg 2+ 消耗的主要机制。然而，早期的影响对肾脏 Mg 2+ 处理的抑制作用尚不清楚。我们在小鼠身上的初步数据支持了在其他动物身上的发现噻嗪类药物会暂时降低而不是增加尿 Mg 2+ 排泄量。基于此我们建议急性 K + 负荷后 Mg 2+ 排泄减少，这会抑制 NCC 促进下游 K + 用于保存血清 Mg 2+ 。相反，肾脏 Mg 2+ 处理在该疾病中显得正常高钾性高血压 (FHHt)，其中 NCC 过度活跃。目标 1 将检验以下假设：在双离合变换中 2 我我 Na+ 重吸收会在 DCT 重塑之前改变 Mg2+ 处理，这在生理学上是可行的相关的。我们将使用 Gitelman 综合征、EAST 综合征、噻嗪类药物的诱导小鼠模型，和 K+ 加载来测试这一点。我们将进行时间过程分析并测量电解质处理的变化，以及具有光学组织透明和 3D 成像的 DCT 结构。低镁血症和低钾血症是临床上常见在一起，例如顺铂化疗后。 K+ 通常难以治疗低钾血症除非低镁血症得到解决，否则应补充补充剂，但其潜在机制尚未阐明决定。目标 2 将测试两种提议的促进连接段 K+ 分泌的机制并得到我们初步数据的支持：(i) K+ 通道 ROMK 的 Mg2+ 依赖性去抑制和 (ii) 增加 DCT 的 Na+ 输送量。我们将确定低镁血症中的 NCC、ENaC 和 ROMK 活性通过进行利尿反应测试，建立了小鼠和新的低镁血症/低钾血症小鼠模型。我们将还测试了补充 Mg2+ 是否可以减轻具有诱导性 NCC 抑制的小鼠模型中的 K+ 损失。已提出顶端 K+ 通道 Kv1.1 产生膜电位，为 Mg2+ 沿 DCT 进入，因为人类 Kv1.1 突变会导致低镁血症。然而，实验缺乏证据。为了测试这一点，在目标 3 中，我们将对新型肾小管特异性 Kv1.1 敲除小鼠进行表型分析，并确定Kv1.1是否决定早期DCT中的顶膜电位。