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Effects of the sodium‐hydrogen exchange inhibitor EIPA on chloride secretion in permeabilized monolayers of chick renal proximal tubule cells
Author(s) -
Anttila Ashley,
Laverty Gary,
Árnason Sighvatur S.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1338-b
Subject(s) - forskolin , amiloride , sodium–hydrogen antiporter , chemistry , endocrinology , medicine , sodium , biophysics , biology , biochemistry , receptor , organic chemistry
In voltage‐clamped cultured monolayers of the chick renal proximal epithelium, parathyroid hormone and the cAMP agonist forskolin stimulate a positive short circuit current (I SC ) that is sensitive to chloride ion (Cl − ) substitution and to Cl − channel blockers, suggesting a stimulated net Cl − secretion. However, this I SC response is also blocked by the Na + /H + exchanger (NHE) inhibitor, 5‐ethylisopropyl amiloride (EIPA), indicating a possible interaction between these two transport pathways. To further study these interactions, we generated current‐voltage curves (I/V curves) on permeabilized monolayers (10 μM amphotericin B to the basolateral side). Control and EIPA (100 μM) pre‐treated monolayers were subsequently treated with 1.0 μM forskolin followed by the Cl − channel blocker NPPB. I/V curves were generated after each addition. Forskolin stimulated I SC (intercept of I/V curves) by 19.4 ± 3.1 μA/cm 2 (n = 7), and EIPA almost completely blocked this effect (0.96 ± 1.27 μA/cm 2 , n = 5). On the other hand, forskolin decreased the I/V curve slope (conductance) by 19 ± 4% in controls, but increased it by 17.18 ± 4.4% in EIPA treated monolayers. Similarly, NPPB had opposite effects on slope with and without EIPA. These data suggest that forskolin may both activate a Cl − secretion pathway and simultaneously inhibit a conductance associated with NHE, and that these two transport components may be linked. Supported by NSF IBN 03433478.