The Principal site of absorption of sodium is

Other than at thin descending limb of the loop of Henle, all other sites of tubule Na+ are reabsorbed by various mechanisms. -        Proximal tubule- 60-70% Na+- H+ exchange Na+- Glucose co-transport Na+- amino acid co-transport Na+ unitransport -        The thick ascending limb of the loop of Henle - 30% Na+- 2Cl-- K+ co-transport -        Early distal tubule- 7% Na+- Cl- co-transport -        Late distal tubule and collecting duct - 3% ENaC channels