title: Evidence for cystic fibrosis transmembrane conductance regulator-dependent sodium reabsorption in kidney, using Cftr(tm2cam) mice.
abstract: The aims of this study were to investigate (a) if renal Na(+) handling was normal in Cftr(tm2cam) delta F508 cystic fibrosis mice, (b) whether adaptation to dietary salt depletion was preserved and (c) whether Cftr(tm2cam) delta F508 mice exhibited enhanced amiloride-sensitive Na(+) absorption. In Na(+)-replete animals (maintained on a 0.32 % NaCl diet) given a 150 mM NaCl i.v. maintenance infusion, there was no difference in fractional Na(+) excretion (FE(Na)) between wild-type (0. 42 +/- 0.06 %, n = 12) and Cftr(tm2cam) delta F508 mice (0.47 +/- 0.13 %, n = 7). Amiloride infusion significantly increased FE(Na) in both wild-type (3.14 +/- 0.83 %, n = 6) and Cftr(tm2cam) delta F508 mice (3. 47 +/- 0.63 %, n = 9), though with no significant difference between genotypes. A 14 day dietary salt restriction (animals maintained on a 0.03 % NaCl diet) and maintenance infusion with a 15 mM NaCl vehicle caused a reduction in FE(Na) to 0.14 +/- 0.05 %, n = 8 in wild-type mice and 0.14 +/- 0.04 %, n = 8 in Cftr(tm2cam) delta F508 mice. No significant difference in the ability to adapt to low salt conditions was apparent comparing the two genotypes. Treatment of salt-restricted mice with amiloride resulted in a blunted natriuresis in both wild-type mice (FE(Na) = 1.10 +/- 0.16 %, n = 7) and Cftr(tm2cam) delta F508 mice (FE(Na) = 1.97 +/- 0.29 %, n = 9). The natriuresis induced by amiloride was significantly greater in Cftr(tm2cam) delta F508 mice than in wild-type controls. In conclusion, Cftr(tm2cam) delta F508 mice exhibit normal renal salt excretion when either salt replete or salt restricted. Enhanced amiloride-sensitive FE(Na) is consistent with increased Na(+) absorption via the amiloride-sensitive sodium channel ENaC, in cystic fibrosis kidney, but this was only observed during salt restriction.
authors.affiliation: Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK. j.kibble@sheffield.ac.uk
authors.forename: J D
authors.initials: JD
authors.lastname: Kibble
authors.forename: A M
authors.initials: AM
authors.lastname: Neal
authors.forename: W H
authors.initials: WH
authors.lastname: Colledge
authors.forename: R
authors.initials: R
authors.lastname: Green
authors.forename: C J
authors.initials: CJ
authors.lastname: Taylor
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002712:Chlorides / Q000652:urine; D003550:Cystic Fibrosis / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004195:Disease Models, Animal; D004232:Diuretics / Q000494:pharmacology; D053503:Epithelial Sodium Channels; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D007677:Kidney Function Tests; D008297:Male; D051379:Mice; D018181:Mice, Inbred CFTR; D008822:Mice, Transgenic; D012964:Sodium / Q000097:blood* / Q000652:urine; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D017673:Sodium Chloride, Dietary / Q000378:metabolism / Q000494:pharmacology
chemical_list: D002712:Chlorides; D004232:Diuretics; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D017673:Sodium Chloride, Dietary; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000584:Amiloride; D012964:Sodium