Immunohistochemical Demonstration of Cl^- Pump in Type A Intercalated Cells of Rat Kidney

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In order to demonstrate the localization of an ethacrynic acid−sensitive Cl^- pump in the rat kidney, immunohistochemical analysis was performed using an anti−Cl^- pump antibody raised against rat brain Cl^- pump protein with confocal laser scanning microscopy.The antibodies against Na⁺, K⁺−ATPase, aquaporin 2 and a type B intercalated cell marker, 43−kDa protein, were also used for comparison.Anti−Cl^- pump antibody recognized a 51−kDa renal protein of the same size as that in the brain on Western blots.Cl^-−pump−like immunoreactivity was observed on the basolateral membranes of 42±3% of cortical collecting duct(CCD)cells and of 38±1% of outer medullar collecting duct(OMCD)cells.Such immunoreactivity in CCD was sometimes co−localized with Na⁺, K⁺−ATPase, but in OMCD, the Cl^- pump−like immunoreactivity co−existed with neither Na⁺, K⁺−ATPase, aquaporin 2 nor the type B intercalated cell marker 43−kDa protein.Thus, the Cl^- pump was demonstrated to be localized on the basolateral membranes of type A intercalated cells of cortical and medullary collecting ducts in the rat kidney.