Potassium

Potassium is a topic covered in the Washington Manual of Medical Therapeutics.

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  • Potassium is the major intracellular cation. Of the 3000–4000 mEq of K+ found in the average human, 98% is sequestered within cells. Thus, although ECF [K+] is normally 3.5–5.0 mEq/L, the intracellular concentration is roughly 150 mEq/L. This difference in ICF and ECF K+ content is maintained by the Na+/K+-adenosine triphosphatase pump.
  • The K+ intake of individuals on an average Western diet is approximately 1 mEq/kg/d, 90% of which is absorbed by the GI tract. Maintenance of the steady state necessitates matching K+ excretion with ingestion.
  • The elimination of potassium occurs predominately through renal excretion at the distal nephron. K+ secretion is enhanced by distal Na+ reabsorption, which generates a lumen-negative gradient and distal urine flow rate.
  • Renal potassium handling is responsive to aldosterone, which stimulates the expression of distal luminal Na+ channels, and the serum potassium concentration. Aldosterone secretion is, in turn, responsive to angiotensin II and hyperkalemia.

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  • Potassium is the major intracellular cation. Of the 3000–4000 mEq of K+ found in the average human, 98% is sequestered within cells. Thus, although ECF [K+] is normally 3.5–5.0 mEq/L, the intracellular concentration is roughly 150 mEq/L. This difference in ICF and ECF K+ content is maintained by the Na+/K+-adenosine triphosphatase pump.
  • The K+ intake of individuals on an average Western diet is approximately 1 mEq/kg/d, 90% of which is absorbed by the GI tract. Maintenance of the steady state necessitates matching K+ excretion with ingestion.
  • The elimination of potassium occurs predominately through renal excretion at the distal nephron. K+ secretion is enhanced by distal Na+ reabsorption, which generates a lumen-negative gradient and distal urine flow rate.
  • Renal potassium handling is responsive to aldosterone, which stimulates the expression of distal luminal Na+ channels, and the serum potassium concentration. Aldosterone secretion is, in turn, responsive to angiotensin II and hyperkalemia.

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