Regulation of ENaC, AE1 and H+ ATPase in renal intercalated cell specific NBCe2 knockout mice (1098.5)

Abstract

Regulation of ENaC, AE1 and H+ ATPase in renal intercalated cell specific NBCe2 knockout mice Fredrik D Pedersen, Jeppe Praetorius and Helle H Damkier, Department of Biomedicine, Health, Aarhus University, Denmark NBCe2 is an electrogenic Na+ HCO3‐ cotransporter expressed in the brain and kidney. In mouse, NBCe2 mRNA is localized in the collecting duct principal cells; however, attempts to locate the protein in mice have been unsuccessful. In humans, immunohistochemical studies localized NBCe2 to the apical membrane of apparent intercalated cells. Mice lacking NBCe2 are hypertensive and have lower urinary pH, but the mechanism behind and cellular origin of this phenotype is unknown.The aim of the study is to define the cell type responsible for development of hypertension in NBCe2 knockout mice.Intercalated cell specific NBCe2 knockout mice (IC‐KO) were generated using the loxP/cre system. Mice expressing cre recombinase driven by the promotor for the intercalated cell H+ ATPase, B1 were crossed with floxed NBCe2 mice.Tail cuff measurements and urine electrolyte analyses revealed no differences in blood pressure or urine composition between the IC‐KO mice and wildtype littermates. However, immunoblot analysis revealed decreased abundance of the membrane transporters AE1, αENaC and H+ ATPase in the IC‐KO mice. Furthermore, immunohistochemical analysis showed increased γENaC abundance in the apical plasma membrane of the IC‐KO mice.In conclusion, the IC‐KO mouse model does not display the hypertensive phenotype of the full NBCe2 knockout mouse. Nevertheless, the changes in abundance and subcellular localization of key renal membrane transporters indicate a significance of NBCe2 in intercalated cells in mice. However, the changes could also reflect the activity of cre recombinase in a subset of cortical principal cells that has been described for the cre mouse.