Page 194 - Color_Atlas_of_Physiology_5th_Ed._-_A._Despopoulos_2003

A. Regulation of extracellular K concentration
+
K +
K +
Dietary uptake
ca. 100 mmol/day Physical work, Hyperkalemia
trauma

Insulin Epinephrine Aldosterone
Intracellular fluid
+
[K ] ≈ 150 mmol/L Na -K -ATPase Extracellular fluid
+
+
+
[K ] = 3.5–4.8mmol/L
K + Na + Potassium Balance I
K +
Acidosis
H + K +
Excretion
+
K channels Plate 7.17
+
B. Resorption and secretion of K in the kidney
LPTP Secretion (with aldosterone)
–20 mV –70 mV
K + K +
H 2 O Na +
? K + K +
K + K + K +
3
1 Proximal tubule cell Principal cell of connecting
K + tubule and connecting duct
Filtrate: 100%
Late proximal: ca. 35%
Early distal: ca. 10–20%
Final urine: 3–200% Reabsorption (without aldosterone)

LPTP H 2 O Cl –
– –
HCO 3 HCO 3
K + K + CA II
+
+
H /K -ATPase
OH +
–
H + CO 2 Na +
H +
K +
K +
K +
2 Thick ascending limb of Henle’s loop
K +
181
4 Type A intercalated cell
Despopoulos, Color Atlas of Physiology © 2003 Thieme
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