Secretin is a key hormone of the intestinal phase of digestion which activates pancreatic, bile duct and Brunner gland HCO(3)^(-) secretion. Recently, the secretin receptor (SCTR) was also found in the basolateral membrane of the beta-intercalated cell (B-IC) of the collecting duct. Experimental addition of secretin triggers a pronounced activation of urinary HCO(3)^(-) excretion, which is fully dependent on key functional proteins of the B-IC, namely apical pendrin and CFTR and the …