title: Mice lacking the basolateral Na-K-2Cl cotransporter have impaired epithelial chloride secretion and are profoundly deaf.
abstract: In chloride-secretory epithelia, the basolateral Na-K-2Cl cotransporter (NKCC1) is thought to play a major role in transepithelial Cl(-) and fluid transport. Similarly, in marginal cells of the inner ear, NKCC1 has been proposed as a component of the entry pathway for K(+) that is secreted into the endolymph, thus playing a critical role in hearing. To test these hypotheses, we generated and analyzed an NKCC1-deficient mouse. Homozygous mutant (Nkcc1(-/-)) mice exhibited growth retardation, a 28% incidence of death around the time of weaning, and mild difficulties in maintaining their balance. Mean arterial blood pressure was significantly reduced in both heterozygous and homozygous mutants, indicating an important function for NKCC1 in the maintenance of blood pressure. cAMP-induced short circuit currents, which are dependent on the CFTR Cl(-) channel, were reduced in jejunum, cecum, and trachea of Nkcc1(-/-) mice, indicating that NKCC1 contributes to cAMP-induced Cl(-) secretion. In contrast, secretion of gastric acid in adult Nkcc1(-/-) stomachs and enterotoxin-stimulated fluid secretion in the intestine of suckling Nkcc1(-/-) mice were normal. Finally, homozygous mutants were deaf, and histological analysis of the inner ear revealed a collapse of the membranous labyrinth, consistent with a critical role for NKCC1 in transepithelial K(+) movements involved in generation of the K(+)-rich endolymph and the endocochlear potential.
authors.affiliation: Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267, USA.
authors.forename: M
authors.initials: M
authors.lastname: Flagella
authors.forename: L L
authors.initials: LL
authors.lastname: Clarke
authors.forename: M L
authors.initials: ML
authors.lastname: Miller
authors.forename: L C
authors.initials: LC
authors.lastname: Erway
authors.forename: R A
authors.initials: RA
authors.lastname: Giannella
authors.forename: A
authors.initials: A
authors.lastname: Andringa
authors.forename: L R
authors.initials: LR
authors.lastname: Gawenis
authors.forename: J
authors.initials: J
authors.lastname: Kramer
authors.forename: J J
authors.initials: JJ
authors.lastname: Duffy
authors.forename: T
authors.initials: T
authors.lastname: Doetschman
authors.forename: J N
authors.initials: JN
authors.lastname: Lorenz
authors.forename: E N
authors.initials: EN
authors.lastname: Yamoah
authors.forename: E L
authors.initials: EL
authors.lastname: Cardell
authors.forename: G E
authors.initials: GE
authors.lastname: Shull
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D001794:Blood Pressure; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D003638:Deafness / Q000209:etiology* / Q000473:pathology; D004064:Digestive System / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism; D005838:Genotype; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters; D015996:Survival Rate
chemical_list: D002352:Carrier Proteins; D002712:Chlorides; D008565:Membrane Proteins; D028021:Sodium-Potassium-Chloride Symporters; D012964:Sodium; D011188:Potassium