Tubular sodium handling along the nephron

At a glance

• The kidneys filter about 24,000 mmol of sodium a day and excrete about 100 to 200 mmol, matching intake. Over 99% is reabsorbed.
• Each segment uses a different apical transporter. Every segment depends on the basolateral Na⁺/K⁺-ATPase.
• Proximal tubule reabsorbs about 65% isotonically; the thick ascending limb 25% (water-impermeable, builds the medullary gradient); the distal convoluted tubule 5 to 7% (dilutes urine); the collecting duct 2 to 3% (fine-tunes under aldosterone).