Specific ion transport mechanisms, particularly apical potassium recycling via channels such as ROMK, establish the lumen-positive electrical potential across the thick ascending loop of Henle.
The retrieved papers consistently confirm that active transcellular transport mechanisms, specifically apical potassium channels (like ROMK) and cotransporters in the thick ascending limb, generate the lumen-positive electrochemical gradient necessary for subsequent paracellular reabsorption.