Cholangiocyte anion exchange and biliary bicarbonate excretion

Figure 1 The major ion carriers implicated in pH_i regulation and secretion of bicarbonate to bile from liver cells. A: Hepatocytes; B: Cholangiocytes.

Figure 2 Hormonal stimulation of bicarbonate excretion from hepatocytes and cholangiocytes. A: In hepatocytes, glucagon may induce an exocytic trafficking of vesicles with the anion exchanger AE2/SLC4A2 and the water channel AQP8, which can results in canalicular bicarbonate-rich hydrocholeresis. MRP2/ABCC2, while being a carrier for organic anions like glutathione rather than an inorganic ion transporter, is hereby depicted because of its possible colocalization with the other two flux proteins; B: In cholangiocytes, secretin induces trafficking of vesicles with the chloride channel CFTR, the anion exchanger AE2/SLC4A2, and the water channel AQP1, and further exocytosis to the lumenal membrane of these cells, which results in ductal bicarbonate-rich hydrocholeresis.