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

Abstract

To functionally characterize transport properties of the apical anion exchanger of rabbit β-intercalated cells, the mean change in anion exchange activity, dpHi/d t(where pHi is intracellular pH), was measured in response to lumen Cl− replacement with gluconate in perfused cortical collecting ducts (CCDs). β-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−. β-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, β-cell apical anion exchange was inhibited by α-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 β-cell apical anion exchanger. Taken together, the results demonstrate a distinct “fingerprint” of the rabbit CCD β-cell apical anion exchanger that is unlike that of other known anion exchangers.

AE4 is a DIDS-sensitive Cl−/HCO 3 − exchanger in the basolateral membrane of the renal CCD and the SMG duct

“…In addition, we note that Cl Ϫ /HCO 3 Ϫ exchange by AE4 is DIDS sensitive (Fig. 5), whereas HCO 3 Ϫ secretion by the CCD is DIDS insensitive (8,9,39).…”

“…B: Northern blot analysis of total RNA prepared from rat tissues and hybridized as in A. Nos. indicate preparation of mRNA from stomach (1), jejunum (2), ileum (3), cecum (4), colon (5), pancreas (6), renal cortex (7), renal outer medulla (8), and renal inner medulla (9). C: primers listed in EXPERIMENTAL PROCEDURES were used to amplify AE4 mRNA by RT-PCR from microdissected nephron segments, and the result of a Southern blot with the AE4 probe is shown.…”

“…Yet, it was reported that expression of the rabbit AE4 in Xenopus oocytes resulted in DIDS-insensitive Cl Ϫ uptake (38). This is a critical point with respect to the possible function of AE4 because the Cl Ϫ /HCO 3 Ϫ exchange activity in the luminal membrane of ␤-intercalated cells is DIDS insensitive (8,9,40). Therefore, we carefully examined the effect of 4,4Ј-diisothiocyanatodihydrostilbene-2,2Ј-disulfonic acid (H 2 DIDS) on AE4 activity.…”

“…The ␤-intercalated cells display the opposite polarity in terms of expression of the H ϩ /HCO 3 Ϫ transporters. The ␤-intercalated cells express a Cl Ϫ /HCO 3 Ϫ exchange activity in the luminal membrane (8,9,39). Accordingly, these cells mediate the bulk of HCO 3 Ϫ secretion by the CCD (22,23,30).…”

Uptake of Aristolochic Acid I into Caco-2 Cells by Monocarboxylic Acid Transporters

“…CHC is an inhibitor of not only some MCTs but also anion exchanger. 24) However, coincubation with DIDS (an anion exchange inhibitor) did not decrease the uptake of AAI ( Table 1). The uptake of AAI from the apical membranes of Caco-2 cells via anion exchanger can be ruled out.…”