Pump:  The Na+/K+/2Cl− transporter in the ascending limb of the loop of Henle helps to create a gradient by shifting Na+ into the medullary interstitium. The thick ascending limb of the loop of Henle is the only part of the nephron lacking in aquaporin—a common transporter protein for water channels.
The Na+/K+/2Cl− transporter in the ascending limb of the loop of Henle plays a crucial role in creating a concentration gradient by moving sodium ions into the medullary interstitium. The thick ascending limb of the loop of Henle is unique among nephron segments because it lacks aquaporin, a protein responsible for water transport.