LOCALIZATION OF THE NA+ H+ EXCHANGER ISOFORM NHE-3 IN RABBIT AND CANINE KIDNEY/

The distribution and subcellular localization of Na+/H+ exchanger isof orm NHE-3 was studied in rabbit and canine kidney using polyclonal ant ibodies to an NHE-3 fusion protein. Western blot analyses were perform ed against microsomal, brush-border, and basolateral membranes isolate d from rabbit kidney cortex, outer medulla, and inner medulla. Immunob lots indicated that NHE-3 antibody recognized a strong band with 95-10 0 kDa molecular mass in cortical microsomes. Subcellular localization studies showed that NHE-3 was expressed in brush-border membranes of k idney cortex. Expression of NHE-3 in the medullary regions was studied by immunoblot analysis of NHE-3 antibody against the microsomal membr anes from the outer and inner medulla. NHE-3 antibody specifically lab elled a 95-100 kDa protein in outer but not inner medulla. Subcellular localization studies demonstrated that NHE-3 is localized to the brus h-border membranes of the outer medulla. Immunoblot analysis against b rush-border membranes from canine kidney cortex and outer medulla demo nstrated the presence of an 83-90 kDa protein. The above experiments s uggest that NHE-3 in rabbit kidney is a 95-100 kDa protein and is expr essed in brush-border membranes of the cortex and outer medulla. The c anine kidney NHE-3 is a 83-90 kDa protein and is expressed in brush-bo rder membranes of the cortex and outer medulla. Based on its subcellul ar localization, we conclude that NHE-3 may be involved in vectorial N a+ and HCO3- transport and pH(0) regulation.