1. Relation between BK-α/β4-mediated potassium secretion and ENaC-mediated sodium reabsorption
- Author
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Huaqing Li, Alan M. Weinstein, Dianelys Rivero-Hernandez, Ryan J. Cornelius, Donghai Wen, Steven C. Sansom, and Yang Yuan
- Subjects
Epithelial sodium channel ,medicine.medical_specialty ,Large-Conductance Calcium-Activated Potassium Channel beta Subunits ,Potassium ,Sodium ,Bicarbonate ,Sodium Chloride Symporter Inhibitors ,ENaC ,chemistry.chemical_element ,K secretion ,030204 cardiovascular system & hematology ,Article ,Amiloride ,03 medical and health sciences ,chemistry.chemical_compound ,Mice ,0302 clinical medicine ,intercalated cell ,Internal medicine ,medicine ,Epithelial Sodium Channel Blockers ,Animals ,TTKG ,Epithelial Sodium Channels ,Large-Conductance Calcium-Activated Potassium Channel alpha Subunits ,030304 developmental biology ,2. Zero hunger ,Mice, Knockout ,0303 health sciences ,Renal sodium reabsorption ,Potassium, Dietary ,Sodium, Dietary ,BK-α/β4 ,Nephrons ,Potassium channel ,3. Good health ,Mice, Inbred C57BL ,Endocrinology ,Hydrochlorothiazide ,chemistry ,Na reabsorption ,Nephrology ,Knockout mouse ,medicine.drug ,math modeling - Abstract
The large-conductance, calcium-activated BK-α/β4 potassium channel, localized to the intercalated cells of the distal nephron, mediates potassium secretion during high-potassium, alkaline diets. Here we determine whether BK-α/β4-mediated potassium transport is dependent on epithelial sodium channel (ENaC)-mediated sodium reabsorption. We maximized sodium-potassium exchange in the distal nephron by feeding mice a low-sodium, high-potassium diet. Wild-type and BK-β4 knockout mice were maintained on a low-sodium, high-potassium, alkaline diet or a low-sodium, high-potassium, acidic diet for 7-10 days. Wild-type mice maintained potassium homeostasis on the alkaline, but not acid, diet. BK-β4 knockout mice could not maintain potassium homeostasis on either diet. During the last 12 h of diet, wild-type mice on either a regular, alkaline, or an acid diet, or knockout mice on an alkaline diet, were administered amiloride (an ENaC inhibitor). Amiloride enhanced sodium excretion in all wild-type and knockout groups to similar values; however, amiloride diminished potassium excretion by 59% in wild-type but only by 33% in knockout mice on an alkaline diet. Similarly, amiloride decreased the trans-tubular potassium gradient by 68% in wild-type but only by 42% in knockout mice on an alkaline diet. Amiloride treatment equally enhanced sodium excretion and diminished potassium secretion in knockout mice on an alkaline diet and wild-type mice on an acid diet. Thus, the enhanced effect of amiloride on potassium secretion in wild-type compared to knockout mice on the alkaline diet clarify a BK- α/β4-mediated potassium secretory pathway in intercalated cells driven by ENaC-mediated sodium reabsorption linked to bicarbonate secretion.
- Published
- 2014