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A cAMP‐activated Cl − channel in the apical membrane of chick ( Gallus gallus ) proximal tubule cells
Author(s) -
Laverty Gary,
Reddy Varudhini,
Árnason Sighvatur S
Publication year - 2010
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.24.1_supplement.610.10
Subject(s) - forskolin , apical membrane , epithelial polarity , bumetanide , cotransporter , chemistry , chloride channel , epithelial sodium channel , medicine , ussing chamber , endocrinology , amiloride , tubule , biophysics , ion transporter , symporter , channel blocker , sodium , biology , secretion , stimulation , biochemistry , calcium , membrane , kidney , transporter , organic chemistry , gene
In primary culture, filter‐grown monolayers from chick renal proximal tubules express a parathyroid hormone‐activated transport current under epithelial voltage clamp conditions. Data suggest that this positive current response is due to Cl − ion transport and is mediated by a cystic fibrosis transmembrane regulator (CFTR)‐like Cl − channel on the apical membrane. To further examine this transport pathway we permeabilized the basolateral membrane of proximal tubule monolayers in Ussing chambers. After establishing either basolateral to apical (Bl > Ap) or apical to basolateral (Ap > Bl) chloride gradients by glutamate substitution, nystatin (300 μg/ml) was added to the basolateral reservoirs. Subsequent stimulation with 1 μM forskolin caused a short circuit current (ΔI SC ) response of 7.67 ± 0.99 and − 19.50 ± 3.54 μA/cm 2 in the Bl > Ap and Ap > Bl monolayers, respectively (means ± SEM, N = 6). Basolateral addition of 100 μM bumetanide, a blocker of the sodium‐potassium‐2 chloride cotransporter, had no effect on these I SC responses, indicating complete basolateral permeabilization. In contrast, apical addition of 20 μM CFTR inhibitor 172 reduced the forskolin‐stimulated I SC by 38 and 48%, for the secretory and reabsorptive gradients, respectively. These data support the hypothesis that chick proximal tubule cells are capable of active, stimulated chloride secretion, mediated by a cAMP‐activated Cl − channel.