Disorders of Potassium: Physiology
Potassium (K+) is the predominant intracellular cation in the body. The intracellular [K+] is 140–150 mEq/L; in blood it is 3.5–5 mEq/L. Serum contains a slightly higher concentration of K+ than plasma because K+ is released from red blood cells during clot formation. Maintenance of a high cellular concentration of K+ is necessary for several cellular functions, including growth, nucleic acid and protein synthesis, and regulation of cell volume, as well as pH and enzyme activation. In addition, a high intracellular concentration of K+ is essential to the maintenance of the resting membrane potential for cellular excitability and contraction. The high intracellular K+ concentration is maintained by the Na/K-ATPase located in the cell membranes of all animal cells. The activity of this enzyme is influenced by a variety of hormones. The kidney is the primary route for K+ excretion. In general, K+ excretion in the urine, called kaliuresis, parallels dietary intake. The other route for K+ excretion is the colon. Under conditions of decreased renal function, K+ excretion by the colon is enhanced.
KeywordsKaliuresis Renal function and potassium Distal nephron Potassium excretion Potassium secretion
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