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Figure 2: This figure shows K+ handling by the kidney. Proximal convoluted tubule: 65% K+ is reabsorbed. Thick ascending loop of Henle: K+ enters the cell via the Na+–K+–2Cl cotransporter. Early distal convoluted tubule: Na+ and Cl reabsorbed by Na+–Cl cotransporter. K+ is secreted into the lumen via the renal outer medullary potassium channel. Late distal convoluted tubule, connecting tubule, and cortical collecting duct: (1) Principal cells: K+ secreted into the lumen by the renal outer medullary potassium channels and K+ maxi conductance channels. Epithelial Na channel shifts Na from the lumen to inside the cell. (2) Intercalated cells Type A: K+ taken up inside the cell from the lumen with the help of K+–H+ exchanger

Figure 2: This figure shows K<sup>+</sup> handling by the kidney. Proximal convoluted tubule: 65% K<sup>+</sup> is reabsorbed. Thick ascending loop of Henle: K<sup>+</sup> enters the cell via the Na<sup>+</sup>–K<sup>+</sup>–2Cl<sup>−</sup> cotransporter. Early distal convoluted tubule: Na<sup>+</sup> and Cl<sup>−</sup> reabsorbed by Na<sup>+</sup>–Cl<sup>−</sup> cotransporter. K<sup>+</sup> is secreted into the lumen via the renal outer medullary potassium channel. Late distal convoluted tubule, connecting tubule, and cortical collecting duct: (1) Principal cells: K<sup>+</sup> secreted into the lumen by the renal outer medullary potassium channels and K<sup>+</sup> maxi conductance channels. Epithelial Na channel shifts Na from the lumen to inside the cell. (2) Intercalated cells Type A: K<sup>+</sup> taken up inside the cell from the lumen with the help of K<sup>+</sup>–H<sup>+</sup> exchanger