Immunocytochemical localization of Na-K-ATPase alpha- and gamma-subunits in rat kidney

The gamma -subunit of the Na-K-ATPase is a single-span membrane protein tha t alters the kinetic properties of the enzyme. It is expressed in the kidne y, but our initial observations indicated that it is not present in all nep hron segments (Arystarkhova E, Wetzel RK, Asinovski NK, and Sweadner KJ. J Biol Chem 274: 33183-33185, 1999). Here we used triple-label confocal immun ofluorescence microscopy in rat kidney with antibodies to Na-KATPase alpha1 - and gamma -subunits and nephron segment-specific markers. Na-K-ATPase alp ha1-subunit stain was low but unambiguous in proximal segments, moderate in macula densa, connecting tubules, and cortical collecting ducts, high in t hick ascending limb and distal convoluted tubules, and nearly undetectable in glomeruli, descending and ascending thin limb, and medullary collecting ducts. The gamma -subunit colocalized at staining levels similar to al-subu nit, in basolateral membranes in all segments except cortical thick ascendi ng limb and cortical collecting ducts, which had alpha1-subunit but no dete ctable gamma -subunit stain. Selective gamma -subunit expression may contri bute to the variations in Na-K-ATPase properties in different renal segment s.