Loop of Henle
Sodium is reabsorbed in the thick ascending limb of loop of Henle, by Na-K-2Cl symporter and Na-H antiporter. It goes against its chemical driving force, but the high electrical driving force renders the overall electrochemical driving force positive anyway, availing some sodium to diffuse passively either the transcellular or paracellular way.
Read more about this topic: Renal Sodium Reabsorption