Parietal cells express high levels of Na-K-2Cl cotransporter on migrating into the gastric gland neck

Na-K-2Cl cotransport and Cl/HCO2 exchange are prominent mechanisms for Cl- uptake in Cl- -secreting epithelial cells. We used immunofluorescence micro scopy to delineate the distributions of Na-K-2Cl cotransporter-l (NKCC1) an d anion exchanger-2 (AE2) proteins in rat gastric mucosa (zymogenic zone). Parietal cells (PCs) above the neck of the gastric gland contained abundant AE2 but little or no NKCC1, whereas those in the neck and base contained h igh NKCC1 but diminished AE2. Lower levels of NKCC1 were detected in surfac e mucous cells and in cells comprising the blind ends of all glands. Pulse labeling of proliferating cells with bromodeoxyuridine indicated that new P Cs originate in the isthmus with scant NKCC1; the subset of PCs that migrat e downward expresses NKCC1 abruptly on entering the neck, within 7 days of cell division. Our results suggest that downwardly migrating PCs replace on e mechanism for Cl- entry (Cl/HCO3 exchange) with another (Na-K-2Cl cotrans port).