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

To functionally characterize transport properties of the apical anion exchanger of rabbit beta-intercalated cells, the mean change in anion exchange activity, dpH(i)/dt (where pH(i) is intracellular pH), was measured in response to lumen Cl(-) replacement with gluconate in perfused cortical collecting ducts (CCDs). beta-Cell epical 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, I 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 IC(50) Of 2.4 mM. Substitution of either sulfate or gluconate for lumen Cl(-) resulted in a similar rate of alkalinization. Conversely, pH(i) 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 knows anion exchangers.