Figure 2.

Cl− transport in intestinal epithelial cells. At the basolateral membrane, Cl− enters the cell from blood across the Na+-K+-2Cl cotransporter. Na is expelled by the Na pump, and K leaves via a K channel. Na is shown crossing the cell layer via a paracellular pathway, but Na channels also exist (not shown). Both cystic fibrosis transmembrane regulator (CFTR) and ClC-2 Cl− channels are present on the apical membrane and can allow Cl− to exit the cell. Reproduced from ref. 122, Cuppoletti J, Malinowska DH, Tewari KP, et al. SPI-0211 activates T84 cell chloride transport and recombinant human ClC-2 chloride currents. Am J Physiol 2004;287:C1173–83.