Furosemide-induced urinary acidification is caused by pronounced H+ secretion in the thick ascending limb.

The loop diuretic furosemide inhibits NaCl reabsorption in the thick ascending limb (TAL). In addition, furosemide acidifies the urine, which is traditionally explained by increased Na+ loading to the distal tubule causing an activation of H+ secretion via H+-ATPase in α-intercalated cells. The inability to acidify urine in response to furosemide serves to diagnose distal renal tubular acidosis (dysfunction of α-intercalated cells).

Basolateral P2X receptors mediate inhibition of NaCl transport in mouse medullary thick ascending limb (mTAL).

Extracellular nucleotides regulate epithelial transport via luminal and basolateral P2 receptors. Renal epithelia express multiple P2 receptors, which mediate significant inhibition of solute absorption. Recently, we identified several P2 receptors in the medullary thick ascending limb (mTAL) including luminal and basolateral P2Y(2) receptors (Jensen ME, Odgaard E, Christensen MH, Praetorius HA, Leipziger J.