Maximum reabsorption of sodium takes place in
(A) Proximal convoluted tubule Transport Proteins Involved in the Movement.of Na+ and CI-Across the Apical Membranes of Renal Tubular Cells.3SiteApical TransporterFunctionProximal tubuleNa/glucose CTNa+ uptake, glucose uptake Na+/Pi CTNa+ uptake, Pi uptake Na+ amino acid CTNa+ uptake, amino acid uptake Na/lactate CTNa+ uptake, lactate uptake Na/H exchangerNa+ uptake, H+ extrusion CI/base exchangerCI- uptakeThick ascending limbNa-K-2CI CTNa+ uptake, CI- uptake, K+ uptake Na/H exchangerNa+ uptake, H+ extrusion K+ channelsK+ extrusion (recycling)Distal convoluted tubuleNaCI CTNa+ uptake, CI- uptakeCollecting ductNa+ channel (ENaC)Na+ uptake# In the proximal tubules, the thick portion of the ascending limb of the loop of Henle, the distal tubules, and the collecting ducts, Na+ moves by cotransport or exchange from the tubular lumen into the tubular epithelial cells down its concentration and electrical gradients and is actively pumped from these cells into the interstitial space. Thus, Na+ is actively transported out of all parts of the renal tubule except the thin portions of the loop of Henle. Na+ is pumped into the interstitium by Na+-K+ ATPase. It extrudes three Na+ in exchange for two K+ that are pumped into the cell.
Proximal convoluted tubule
Distal convoluted tubule
Loop of Henle
Collecting duct
Misc.