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Abstract: FR-OR42

Dietary Anion Controls Potassium Excretion: It’s More Than a Poorly Absorbable Anion Effect

Session Information

Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders

  • 1001 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Basic


  • Al-Qusairi, Lama, Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Grimm, Rick, Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Zapf, Ava M., Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Tahaei, Seyedmohammadebrahim, Johns Hopkins Medicine, Baltimore, Maryland, United States
  • Abood, Delaney C., Emory University, Atlanta, Georgia, United States
  • Wall, Susan M., Emory University, Atlanta, Georgia, United States
  • Welling, Paul A., Johns Hopkins Medicine, Baltimore, Maryland, United States

Aldosterone-dependent and -independent mechanisms are known to orchestrate potassium excretion in the distal nephron (DN). In the latter, potassium secretion, mediated by ROMK and BK channels, is dependent on lumen-negative transepithelial potential established by ENaC. Poorly absorbable anions, including HCO3-, are thought to increase K+secretion by hyperpolarizing the membrane potential, but accumulating data indicate luminal anions may also directly influence the expression of the potassium secretory machinery.


Here we characterize the anion effect in wild-type mice randomized to control, or high KCl or high KHCO3 diets, and explore mechanisms in knockout mice, lacking aldosterone synthase (AS-KO) or the chloride-bicarbonate exchanger, pendrin (Pds-KO).


Consumption of the high KHCO3 diet increased urinary potassium K+ excretion and the trans-tubular K+ gradient (TTKG) significantly more than high KCl diet. Although both diets increased ENaC expression and proteolytic activation and increased ROMK protein abundance and apical membrane expression in the early connecting tubule (CNT), the responses were significantly more pronounced with consumption of the high KHCO3 diet, despite elevating aldosterone to similar levels. Compared to the more restricted response in the early CNT with the high KCl diet, the high KHCO3 diet increased apical membrane ROMK along the entire CNT. In addition, the high KHCO3 diet uniquely increased the abundance of the BK potassium channel b4 subunit, which stabilizes BKa channel membrane localization. Studies in AS-KO mice revealed the stimulatory effects of high KHCO3 diet on ROMK are not dependent on aldosterone. The KHCO3diet also uniquely upregulated the Cl-/HCO3- exchanger, pendrin, and studies in pendrin KO mice revealed that pendrin deletion blunted the increase in the TTKG specific to the KHCO3 condition.


In summary, bicarbonate stimulates potassium excretion beyond a non-absorbable anion effect, increasing ENaC cleavage, and apical membrane expression of ROMK and pendrin. The latter plays a significant role in K+ secretion by providing the luminal HCO3-. The response provides an adaptive mechanism to prevent hyperkalemia and alkalosis while consuming alkaline-ash rich diets.


  • NIDDK Support