IMMUNOLOCALIZATION OF THE NA+ H+ EXCHANGER ISOFORM NHE2 IN RAT-KIDNEY/

Four Na+/H+ exchangers (NHE1 to NHE4) have been detected in the kidney . Renal NHE2 expression sites have not been fully established. We have raised rabbit antisera against an oligopeptide related to the amino a cids 652 to 661 of rat NHE2. Western blot analysis of plasma membrane fractions isolated from rat renal cortex showed that affinity-purified anti-NHE2 antibody detected an 85-kDa protein in apical but not in ba solateral membranes. The labeling of this 85-kDa protein was specifica lly blocked by preincubation of the antibody with its monomeric peptid e, indicating specific recognition. Indirect immunolabeling was perfor med on sections of paraformaldehyde-fixed rat kidney embedded in paraf fin. Strong staining was seen in the apical membrane of cortical thick ascending limbs, distal convoluted tubules, and connecting tubules. M uch weaker apical staining was found in medullary thick ascending limb s of Henle. In the inner medulla, some thin limbs were intensively lab eled by the anti-NHE2 antibody. No staining could be detected in any s egments of the proximal tubule and collecting duct.