Figure 1.

Ionic pathways taken into account in the model of HBE. Apical ion channels for Cl⁻, ${\text{HCO}}_3^{-}$ Na⁺, and K⁺ are considered, as are the basolateral Cl⁻ and K⁺ channels. The basolateral NaK pump and the NKCC are reminiscent of the previous model. NHE, AE, and NBC are included in the version of the model introduced here. HSC, highly selective channel; NSC, nonselective channel; CNG, cyclic nucleotide-gated channel; NaK-P, sodium potassium pump.