Figure 10.

Model of countercurrent transport of ammonia in the outer medulla. Ammonia absorbed by the mTAL is recycled either into the S3 portion of the proximal tubule and descending thin limb of the loop of Henle, a process that plays an important role in generating the corticomedullary ammonia concentration gradient. In addition, a portion of the ammonia absorbed into the interstitium by the mTAL is secreted into the lumen of the outer medullary collecting duct. The expression of SLC4A11 in the descending thin limb of long‐looped nephrons provides a pathway for ammonia recycling in this segment. DTL_OM, long‐looped descending thin limb of the outer medulla.