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XB-ART-36044
J Membr Biol 2007 Feb 01;2152-3:195-204. doi: 10.1007/s00232-007-9018-z.
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Inhibition of the Na/bicarbonate cotransporter NBCe1-A by diBAC oxonol dyes relative to niflumic acid and a stilbene.

Liu X , Williams JB , Sumpter BR , Bevensee MO .


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Na/HCO(3) cotransporters (NBCs) are important regulators of intracellular pH (pH(i) in a variety of organ systems where acid-base status is critical for tissue function. To characterize the pharmacology of NBCs in more detail, we used the two-electrode voltage-clamp technique to examine the effect of previously identified inhibitors of anion exchanger 1 (AE1) on the activity of rat NBCe1-A expressed in Xenopus laevis oocytes. NBC-expressing oocytes voltage-clamped at -60 mV and exposed to a 5% CO(2)/33 mM HCO(3)(-) solution displayed NBC-mediated outward currents that were inhibited by either niflumic acid or one of the two bis-oxonol dyes diBA(3)C4 and diBA(5)C4. NBCe1-A was less sensitive to niflumic acid (apparent K(i) of 100 microM) than 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, apparent K(i) of 36 microM) but more sensitive to the diBAC dyes (apparent K(i) of approximately 10 microM). Based on current-voltage relationships, the diBAC dyes inhibited HCO(3)(-) -induced NBCe1-mediated inward currents more so than outward currents. NBCe1 sensitivity to the dyes was (1) lower in the presence of 40 microM DIDS, (2) unaffected by changes in external HCO(3)(-) concentration and (3) only modestly higher at an external Na(+) concentration of 5, but not 15 or 33, mM. Therefore, the diBAC dyes compete with DIDS but not appreciably with Na(+) or HCO(3)(-) for binding. The mechanism of diBAC inhibition of NBCe1 appears similar to that previously reported for AE1.

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Species referenced: Xenopus laevis
Genes referenced: bag3 slc4a1 slc4a4

References [+] :
Alper, Differential inhibition of AE1 and AE2 anion exchangers by oxonol dyes and by novel polyaminosterol analogs of the shark antibiotic squalamine. 1998, Pubmed, Xenbase