膳食中摄入大量 K+ 会抑制近端肾小管的转运。

IF 3.7 2区 医学 Q1 PHYSIOLOGY American Journal of Physiology-renal Physiology Pub Date : 2023-08-01 Epub Date: 2023-06-15 DOI:10.1152/ajprenal.00013.2023
Tong Wang, Tommy Liu, Shuhua Xu, Gustavo Frindt, Alan M Weinstein, Lawrence G Palmer
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引用次数: 0

摘要

采用自由流微量穿刺法测量了慢性饮食 K+ 负荷对大鼠近端肾小管(PT)功能的影响,同时还测量了大鼠的整体肾功能,包括尿量、肾小球滤过率以及 Na+ 和 K+ 的绝对排泄量和部分排泄量。与食用1%氯化钾[控制K+ (CK)]饮食的大鼠相比,连续7天给动物喂食含5%氯化钾[高K+ (HK)]的饮食可使肾小球滤过率降低29%,尿量增加77%,K+绝对排泄量增加202%。HK 不会改变 Na+ 的绝对排泄量,但会显著增加 Na+ 的部分排泄量(1.40% 对 0.64%),这表明 HK 会减少 Na+ 的部分吸收。在麻醉动物中使用自由流微量穿刺法评估 PT 重吸收。在 PT 可触及长度的 80% 处,菊粉浓度的测量结果表明,CK 和 HK 的体积重吸收率分别为 73% 和 54%。在同一部位,CK 动物的 PT Na+ 重吸收分数为 66%,HK 动物为 37%。CK 和 HK 的 PT K+ 重吸收率分别为 66% 和 37%。为了评估Na+/H+交换异构体3(NHE3)在介导这些变化中的作用,我们使用Western印迹法测定了总肾微粒体和表面膜中NHE3蛋白的表达。我们发现这两种细胞组分中的蛋白质均无明显变化。Ser552 磷酸化形式的 NHE3 在 CK 和 HK 动物中的表达也相似。PT转运的减少可能会促进K+的排泄,并通过将Na+的重吸收从K+重吸收肾段转移到K+分泌肾段来帮助平衡Na+的排泄。 在喂食富含K+饮食的大鼠中,近端肾小管重吸收的液体、Na+和K+与对照饮食的动物相比要少。肾小球滤过率也有所下降,这可能是由于肾小球-肾小管反馈所致。这些减少可能有助于通过将 Na+ 的重吸收转移到分泌 K+ 的肾小球区段来同时维持这两种离子的平衡。
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High dietary K+ intake inhibits proximal tubule transport.

The impact of chronic dietary K+ loading on proximal tubule (PT) function was measured using free-flow micropuncture along with measurements of overall kidney function, including urine volume, glomerular filtration rate, and absolute and fractional Na+ and K+ excretion in the rat. Feeding animals a diet with 5% KCl [high K+ (HK)] for 7 days reduced glomerular filtration rate by 29%, increased urine volume by 77%, and increased absolute K+ excretion by 202% compared with rats on a 1% KCl [control K+ (CK)] diet. HK did not change absolute Na+ excretion but significantly increased fraction excretion of Na+ (1.40% vs. 0.64%), indicating that fractional Na+ absorption is reduced by HK. PT reabsorption was assessed using free-flow micropuncture in anesthetized animals. At 80% of the accessible length of the PT, measurements of inulin concentration indicated volume reabsorption of 73% and 54% in CK and HK, respectively. At the same site, fractional PT Na+ reabsorption was 66% in CK animals and 37% in HK animals. Fractional PT K+ reabsorption was 66% in CK and 37% in HK. To assess the role of Na+/H+ exchanger isoform 3 (NHE3) in mediating these changes, we measured NHE3 protein expression in total kidney microsomes as well as surface membranes using Western blots. We found no significant changes in protein in either cell fraction. Expression of the Ser552 phosphorylated form of NHE3 was also similar in CK and HK animals. Reduction in PT transport may facilitate K+ excretion and help balance Na+ excretion by shifting Na+ reabsorption from K+-reabsorbing to K+-secreting nephron segments.NEW & NOTEWORTHY In rats fed a diet rich in K+, proximal tubules reabsorbed less fluid, Na+, and K+ compared with those in animals on a control diet. Glomerular filtration rates also decreased, probably due to glomerulotubular feedback. These reductions may help to maintain balance of the two ions simultaneously by shifting Na+ reabsorption to K+-secreting nephron segments.

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来源期刊
CiteScore
8.40
自引率
7.10%
发文量
154
审稿时长
2-4 weeks
期刊介绍: The American Journal of Physiology - Renal Physiology publishes original manuscripts on timely topics in both basic science and clinical research. Published articles address a broad range of subjects relating to the kidney and urinary tract, and may involve human or animal models, individual cell types, and isolated membrane systems. Also covered are the pathophysiological basis of renal disease processes, regulation of body fluids, and clinical research that provides mechanistic insights. Studies of renal function may be conducted using a wide range of approaches, such as biochemistry, immunology, genetics, mathematical modeling, molecular biology, as well as physiological and clinical methodologies.
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