Fig. 11. Model of transporter distribution in enterocytes of killifish intestinal epithelium, showing brush border (BB) on the luminal side and cells overlying the basement membrane (BM) on the serosal side. In the model, all cells have Na⁺/K⁺-ATPase only in the basolateral membrane. The cell on the left is modelled for uptake of ions and fluid, while that on the right is modelled for secretion. The Na⁺/K⁺/2Cl^– cotransporter (NKCC) is present in the basal portion of all enterocytes and, in most cells (left), also in the apical brush-border membrane. Cystic fibrosis transmembrane conductance regulator (CFTR) immunofluorescence is present in the basal portion of most cells (left) and in the apical membrane of some enterocytes (right).