Distribution of ion transporters and channels in the BECs (A) and in the CP epithelium (B). Only those transporters and channels that play a role in vectorial transport of Na+, Cl-, HCO3- and K+ are shown. These include Na+, K+-ATPase, potassium channels Kir and Kv, chloride/bicarbonate channel Clir and members of the SLC: Na+, HCO3- cotransporters 1 and 2 (NBCn1 and 2), Cl-, HCO3- exchangers 1 and 2 (Ae 1 (in the BBB, figure A) and Ae2 (in the CP, figure B), Na+, H+ exchanger 1 and 2 (Nhe1 and Nhe2), K+-Cl--cotransporters 3 and 4 (KCC3 and 4, in the CP, figure B), Na+-K+-2Cl- cotransporter 1 (NKCC1, in the BBB, figure A) and electrogenic Na+, HCO3- exchanger (NBCe2, in the CP, figure B). In addition, localization of two carbonic anhydrase isoenzymes in the CP epithelium (figure B), CA2 and CA12 are shown, as well as localization of aquaporin 1 (AQP1). Symbol * indicates that NBCn1 was detected in CPE, but it probably does not play a role in vectorial transport of these two ions.