Figure 34.

Role of NBCn1 in the renal medulla. To avoid absorption of ammonia into the blood, NH₄ traveling along the nephron bypasses the renal cortex by passing through the medullary interstitium to the collecting tubules. NH₄⁺ enters thick ascending limb epithelia via K⁺ channels (ROMK) and the Na/K/Cl cotransporter. NH₃ is absorbed across the basolateral membrane into the medullary interstitium, perhaps via a channel. Residual H⁺ is extruded by NHE and titrated by HCO₃⁻ that enters the cell via NBCn1. The basolateral Na-pump has been omitted for clarity.