Transport characteristics of the apical anion exchanger of rabbit cortical collecting duct beta-cells.

To functionally characterize transport properties of the apical anion exchanger of rabbit beta-intercalated cells, the mean change in anion exchange activity, dpHi/dt (where pHi is intracellular pH), was measured in response to lumen Cl- replacement with gluconate in perfused cortical collecting ducts (CCDs). beta-Cell apical anion exchange was not affected by 15-min exposure to 0.2 mM lumen DIDS in the presence of 115 mM Cl-. In contrast, apical anion exchange was significantly inhibited by 0.1 mM lumen DIDS in the absence of Cl-. beta-Cell apical anion exchange was unchanged by 15 mM maleic anhydride, 10 mM phenylglyoxal, 0.2 mM niflumic acid, 1 mM edecrin, 1 mM furosemide, 1 mM probenecid, or 0.1 mM diphenylamine-2-carboxylate. However, beta-cell apical anion exchange was inhibited by alpha-cyano-4-hydroxycinnamic acid, with an IC50 of 2.4 mM. Substitution of either sulfate or gluconate for lumen Cl- resulted in a similar rate of alkalinization. Conversely, pHi was unchanged by substitution of sulfate for lumen gluconate, confirming the lack of transport of sulfate on the beta-cell apical anion exchanger. Taken together, the results demonstrate a distinct "fingerprint" of the rabbit CCD beta-cell apical anion exchanger that is unlike that of other known anion exchangers.