The renal proximal tubule: a model for diversity of anion exchangers and stilbene-sensitive anion transporters.

Abstract

The prototype of plasma membrane anion exchangers is erythrocyte Band 3 (44,47,70). Erythrocyte Band 3 mediates the electroneutFall: 1 exchange of monovalent anions such as Cland HC03 -. Band): can also mediate the electroneutral cotransport of H + and S04 = in exchange for monovalent anions such as Cl-. All known transport modes of Band 3 are inhibited with high affinity by disulfonic stilbenes. In recent years anion transport systems with one or more major properties of Band 3, such as ability to mediate anion exchange and/or sensitivity to inhibition by disulfonic stilbenes, have been demonstrated in the plasma membranes of nonerythroid cells (44). Interestingly, the anion transport systems described in nonerythroid cells have been heterogeneous with respect to substrate and inhibitor affinities, suggesting that there exist several distinct transporters functionally related to Band 3 . On the other hand, such apparent heterogeneity may be a function of the varying conditions and methods that have been used to study anion transport in different cells and tissues. Actual diversity of Band 3-related transporters can be most cJ'earIy demonstrated when it is confirmed by several methods in a single cell type. In this regard, the mammalian proximal tubule has served as a useful model system for revealing the surprising diversity of anion exchangers and stilbene-sensitive anion transporters found in nonerythroid cells. In this review, the properties