Inhibition of bicarbonate transport in peanut lectin-positive intercalated cells by a monoclonal antibody.

Abstract

Intercalated cells (ICC) of the collecting duct are believed to secrete acid (alpha-type) or HCO3 (beta-type). Although these two types of ICC are functionally mirror images of each other, several components in their cell membranes are clearly unique. As a first step in defining the molecular composition of beta-ICC membranes, we raised cell-specific monoclonal antibodies (MAb) against surface antigens. One of these MAb, designated B63, reacts with the apical membrane of peanut lectin agglutinin (PNA)-positive cells of the kidney cortex. B63-positive cells do not react with antibodies against band 3 (the basolateral C1/HCO3 exchanger) or ST.48, markers for alpha-ICC and principal cells, respectively. Despite a significant positive correlation between PNA and B63 staining intensities, determined by flow cytometry, these markers react with separate antigens, as indicated by competition studies and the different distribution of the two antigens. In addition to renal beta-ICC, B63 antigen is present in tissues that are involved in HCO3 secretion, such as the pancreas, salivary glands, and the small intestine, suggesting that it might play a role in HCO3 secretion. To test this hypothesis more directly, we tested the effect of MAb B63 on HCO3 secretion and on changes in intracellular pH (pHi) in isolated perfused cortical collecting ducts. Luminal Cl removal in the presence of luminal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid resulted in a reversible increase in pHi. Luminal application of MAb B63 prevented this change in pHi. MAb B63 also significantly inhibited (by 37.7 +/- 7.3%) HCO3 secretion by isolated perfused tubules, whereas another MAb (MAb 601), which reacts with a separate antigen on beta-ICC, did not alter HCO3 secretion or pHi. These results indicate that B63 antigen plays an important role in HCO3 secretion: it might be either the apical anion exchanger of beta-ICC or an associated regulatory protein.