Regulation of Potassium (K+) Balance

1. Importance of K+
1. K+ is primary CATION (+) in within cells
2. K+ abnormalities cause changes in Resting Mem Pot (neurons, cardiac muscle especially)
2. Renal Control of K+ Levels
1. 10-15% constantly lost in urine
2. most resorption occurs in Proximal Tubule
3. regulation - changing amount SECRETED into urine in the collecting tubules
• low K+ ----> less secretion (intercalated cells in collecting tube can reabsorb more)
• high K+ ----> more secretion
3. Factors Controlling K+ Secretion
1. tubule cell intracellular K+ level - when low, secrete less; when high, secrete more
2. aldosterone level - K+ secreted: Na+ reabsorbed
• increase aldosterone -> more K+ secretion
• decrease aldosterone -> less K+ secretion
3. 3. pH - K+ and H+ compete for antiport with Na+
• lower pH (high H+) -> less K+ secretion
• higher pH (low H+) -> more K+ secretion

Category: Physiology Notes