title: ENaC inhibition stimulates Cl- secretion in the mouse cortical collecting duct through an NKCC1-dependent mechanism.
abstract: In cortical collecting ducts (CCDs) perfused in vitro, inhibiting the epithelial Na(+) channel (ENaC) reduces Cl(-) absorption. Since ENaC does not transport Cl(-), the purpose of this study was to determine how ENaC modulates Cl(-) absorption. Thus, Cl(-) absorption was measured in CCDs perfused in vitro that were taken from mice given aldosterone for 7 days. In wild-type mice, we observed no effect of luminal hydrochlorothiazide on either Cl(-) absorption or transepithelial voltage (V(T)). However, application of an ENaC inhibitor [benzamil (3 μM)] to the luminal fluid or application of a Na(+)-K(+)-ATPase inhibitor to the bath reduced Cl(-) absorption by ∼66-75% and nearly obliterated lumen-negative V(T). In contrast, ENaC inhibition had no effect in CCDs from collecting duct-specific ENaC-null mice (Hoxb7:CRE, Scnn1a(loxlox)). Whereas benzamil-sensitive Cl(-) absorption did not depend on CFTR, application of a Na(+)-K(+)-2Cl(-) cotransport inhibitor (bumetanide) to the bath or ablation of the gene encoding Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1) blunted benzamil-sensitive Cl(-) absorption, although the benzamil-sensitive component of V(T) was unaffected. In conclusion, first, in CCDs from aldosterone-treated mice, most Cl(-) absorption is benzamil sensitive, whereas thiazide-sensitive Cl(-) absorption is undetectable. Second, benzamil-sensitive Cl(-) absorption occurs by inhibition of ENaC, possibly due to elimination of lumen-negative V(T). Finally, benzamil-sensitive Cl(-) flux occurs, at least in part, through transcellular transport through a pathway that depends on NKCC1.
authors.affiliation: Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Pech
authors.forename: Monika
authors.initials: M
authors.lastname: Thumova
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Diana
authors.initials: D
authors.lastname: Agazatian
authors.forename: Edith
authors.initials: E
authors.lastname: Hummler
authors.forename: Bernard C
authors.initials: BC
authors.lastname: Rossier
authors.forename: Alan M
authors.initials: AM
authors.lastname: Weinstein
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nanami
authors.forename: Susan M
authors.initials: SM
authors.lastname: Wall
mesh_terms: D000042:Absorption / Q000187:drug effects; D000450:Aldosterone / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism; D006852:Hydrochlorothiazide / Q000494:pharmacology; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D012964:Sodium / Q000378:metabolism; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*; D064506:Solute Carrier Family 12, Member 2
chemical_list: D002712:Chlorides; D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; C578878:Slc12a2 protein, mouse; D049993:Sodium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; C013407:benzamil; D006852:Hydrochlorothiazide; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium