Postnatal disappearance of type A intercalated cells in carbonic anhydraseII-deficient mice

Despite chronic acidosis, collecting ducts in adult carbonic anhydrase II-d eficient (CAD mice) are depleted of intercalated cells, including those of type A, which are acid-secreting cells. We hypothesized that this depletion could occur during postnatal development. Principal cells were identified by immunofluorescence using an antibody to rat aquaporin-2 (AQP-2), and typ e A intercalated cells using an antibody specific for anion exchanger (AE1) . In CAD mice the proportion of AQP2 positive cells, normal at Ii days, inc reased progressively in the cortical (CCD) and outer medullary collecting d uct (OMCD), to reach almost 100% in the OMCD in adults. The percentage of A E1-positive cells in the OMCD of CAD mice decreased by half by 6 weeks of a ge and further by adulthood. In controls, however, the proportion of AQP2-p ositive cells and that of AE1 positive cells in the OMCD remained stable af ter 10 days of age. AE1-positive cells accounted for the majority of interc alated cells in the OMCD. The mechanisms leading to selective postnatal cel l depletion in the collecting duct in CAD mice remain to be determined.