title: Ontogeny of apical membrane ion conductances and channel expression in cortical collecting duct cells.
abstract: Ontogeny of apical-basolateral epithelial cell polarity was studied by a comparison of embryonic ureteric bud (UB) and mature cortical collecting duct (CCD) primary cultures. Patch-clamp techniques were applied to identify apical ion channels and to measure specific conductance (in nS/10 pF) of the apical membrane (ga) and of the whole cell (Gw). In UB, Gw (1.3 +/- 0.17; n = 32) and ga (1.4 +/- 0.15; n = 9) were not different, whereas they differed greatly in CCD (Gw: 0.79 +/- 0.07, n = 35; ga: 2.3 +/- 0.38, n = 9). In UB, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) (100 microM) similarly reduced ga and Gw by 0.66 +/- 0.21 (n = 9) and 0.48 +/- 0.07 (n = 7), respectively, whereas DIDS had no effect in CCD. Amiloride (1 mM) did not alter UB conductance, whereas, in CCD, ga was more reduced than Gw (0.75 +/- 0.18, n = 8, vs. 0.22 +/- 0.10, n = 7). In addition to this Na(+)-selective conductance, a nonselective cation (NSC) conductance was enriched sixfold in the apical membrane of CCD, possibly due to apical 9 +/- 1-pS (n = 7) NSC channels, whereas UB apical NSC conductance was low. Apical 16 +/- 2-pS (n = 6) K+ channels were identified in CCD but not in UB. The comparison of both developmental states suggests a differentiation of the apical membrane during UB to CCD ontogeny.
authors.affiliation: Physiologisches Institut, Universität München, Germany.
authors.forename: S M
authors.initials: SM
authors.lastname: Huber
authors.forename: M F
authors.initials: MF
authors.lastname: Horster
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000450:Aldosterone / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004553:Electric Conductivity; D004622:Embryo, Mammalian / Q000502:physiology / Q000648:ultrastructure; D005314:Embryonic and Fetal Development; D007473:Ion Channels / Q000378:metabolism* / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000196:embryology* / Q000254:growth & development / Q000502:physiology*; D008854:Microscopy, Electron; D018408:Patch-Clamp Techniques; D051381:Rats / Q000196:embryology
chemical_list: D007473:Ion Channels; D005576:Colforsin; D000450:Aldosterone; D000584:Amiloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium