title: Immunocytochemical response of type A and type B intercalated cells to increased sodium chloride delivery.
abstract: Two populations of intercalated cells, type A and type B, are present in the rat cortical collecting duct (CCD). Type A cells are involved in proton secretion and contain an apical H(+)-adenosinetriphosphatase (ATPase) and a basolateral Cl(-)-HCO3- exchanger. Type B cells are believed to be involved in HCO3- secretion, which is mediated by a Cl(-)-HCO3- exchange process and is Cl- dependent. The aim of this study was to examine the morphological and immunocytochemical response of type B intercalated cells in the rat to increased delivery of Cl- to the CCD. This was accomplished by chronic infusion of a loop diuretic, bumetanide (30 mg.kg body wt-1.day-1), via an osmotic minipump, and simultaneous administration of 0.9% sodium chloride in the drinking water for 6 days. The kidneys were preserved by in vivo perfusion with a periodate-lysine-paraformaldehyde fixative and processed for horseradish peroxidase and protein A gold immunocytochemistry, using rabbit polyclonal antibodies against carbonic anhydrase II, proton ATPase, and band 3 protein. Chronic infusion of bumetanide in combination with a high salt intake was associated with significant changes in the intercalated cells. Type B cells were increased in size and exhibited numerous apical microvilli, increased basolateral membrane area, and marked cytoplasmic and basolateral labeling for H(+)-ATPase. In contrast, type A cells were small and had sparse apical microprojections. H(+)-ATPase immunolabeling was observed primarily over apical tubulovesicles, and there was decreased basolateral immunolabeling for band 3 protein and occasional labeling for band 3 in lysosome-like structures. These observations support the hypothesis that increased delivery of Cl- to the CCD is associated with stimulation of type B intercalated cells to secrete HCO3-. The observations in type A cells are consistent with the cells being in a resting or inactivated state.
authors.affiliation: Laboratory of Experimental Morphology and Cell Biology, University of Florida, Gainesville 32610-0224.
authors.forename: J
authors.initials: J
authors.lastname: Kim
authors.forename: W J
authors.initials: WJ
authors.lastname: Welch
authors.forename: J K
authors.initials: JK
authors.lastname: Cannon
authors.forename: C C
authors.initials: CC
authors.lastname: Tisher
authors.forename: K M
authors.initials: KM
authors.lastname: Madsen
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000032:analysis; D002256:Carbonic Anhydrases / Q000032:analysis; D007150:Immunohistochemistry; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D012965:Sodium Chloride / Q000494:pharmacology*
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D012965:Sodium Chloride; D000251:Adenosine Triphosphatases; D002256:Carbonic Anhydrases