CFTR mediates electrogenic chloride secretion in mouse inner medullary collecting duct (mIMCD-K2) cells

1995 ◽  
Vol 269 (3) ◽  
pp. C683-C689 ◽  
Author(s):  
D. Vandorpe ◽  
N. Kizer ◽  
F. Ciampollilo ◽  
B. Moyer ◽  
K. Karlson ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Patch Clamp ◽  
Collecting Duct ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Inner Medullary Collecting Duct ◽  
Cl Channel ◽  
Cl Channels ◽  
Medullary Collecting Duct ◽  
Cystic Fibrosis Transmembrane

Previously we demonstrated that the inner medullary collecting duct cell line mIMCD-K2 secretes Cl- by an electrogenic mechanism [N. L. Kizer, B. Lewis, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F347-F355, 1995; N. L. Kizer, D. Vandorpe, B. Lewis, B. Bunting, J. Russell, and B. A. Stanton. Am. J. Physiol. 268 (Renal Fluid Electrolyte Physiol. 37): F854-F861, 1995]. The goal of the present study was to characterize the Cl- channel responsible for adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated Cl- secretion. To this end, using the patch-clamp technique, we measured Cl- currents. In whole cell patch-clamp experiments, 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP) activated Cl- currents that were time and voltage independent, inhibited by diphenylamine 2-carboxylate (DPC), and had a linear current-voltage (I-V) relation. In cell-attached patches of the apical membrane, we identified 7-pS Cl- channels that were stimulated by CPT-cAMP. In inside-out patches with Cl- in the pipette and bath solutions, Cl- currents had a linear I-V relation. The halide permeability sequence was PCl = PBr > PI. The Cl- channel inhibitors DPC, 5-nitro-2-(3-phenylpropylamino)-benzoic acid, and glibenclamide blocked the 7-pS Cl- channel, whereas 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid was ineffective. By reverse transcriptase polymerase chain reaction, we isolated a partial cDNA clone encoding the cystic fibrosis transmembrane conductance regulator in mIMCD-K2 cells. We conclude that cAMP stimulates electrogenic Cl- secretion in inner medullary collecting duct cells by activating cystic fibrosis transmembrane conductance regulator Cl- channels.

scholarly journals Effect of ATP-sensitive K+ channel regulators on cystic fibrosis transmembrane conductance regulator chloride currents.

1992 ◽  
Vol 100 (4) ◽  
pp. 573-591 ◽  
Author(s):  
D N Sheppard ◽  
M J Welsh
Keyword(s):  
Cystic Fibrosis ◽  
Voltage Dependence ◽  
K Channel ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
K Channels ◽  
Intracellular Atp ◽  
Cl Channel ◽  
Cl Channels ◽  
Cystic Fibrosis Transmembrane

The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl- channel that is regulated by cAMP-dependent phosphorylation and by intracellular ATP. Intracellular ATP also regulates a class of K+ channels that have a distinct pharmacology: they are inhibited by sulfonylureas and activated by a novel class of drugs called K+ channel openers. In search of modulators of CFTR Cl- channels, we examined the effect of sulfonylureas and K+ channel openers on CFTR Cl- currents in cells expressing recombinant CFTR. The sulfonylureas, tolbutamide and glibenclamide, inhibited whole-cell CFTR Cl- currents at half-maximal concentrations of approximately 150 and 20 microM, respectively. Inhibition by both agents showed little voltage dependence and developed slowly; > 90% inhibition occurred 3 min after adding 1 mM tolbutamide or 100 microM glibenclamide. The effect of tolbutamide was reversible, while that of glibenclamide was not. In contrast to their activating effect on K+ channels, the K+ channel openers, diazoxide, BRL 38227, and minoxidil sulfate inhibited CFTR Cl- currents. Half-maximal inhibition was observed at approximately 250 microM diazoxide, 50 microM BRL 38227, and 40 microM minoxidil sulfate. The rank order of potency for inhibition of CFTR Cl- currents was: glibenclamide < BRL 38227 approximately equal to minoxidil sulfate > tolbutamide > diazoxide. Site-directed mutations of CFTR in the first membrane-spanning domain and second nucleotide-binding domain did not affect glibenclamide inhibition of CFTR Cl- currents. However, when part of the R domain was deleted, glibenclamide inhibition showed significant voltage dependence. These agents, especially glibenclamide, which was the most potent, may be of value in identifying CFTR Cl- channels. They or related analogues might also prove to be of value in treating diseases such as diarrhea, which may involve increased activity of the CFTR Cl- channel.

Chloride channels in the apical membrane of normal and cystic fibrosis airway and intestinal epithelia

1992 ◽  
Vol 263 (1) ◽  
pp. L1-L14 ◽  
Author(s):  
M. P. Anderson ◽  
D. N. Sheppard ◽  
H. A. Berger ◽  
M. J. Welsh
Keyword(s):  
Cystic Fibrosis ◽  
Chloride Channels ◽  
Apical Membrane ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Intestinal Epithelia ◽  
Cl Channel ◽  
Cystic Fibrosis Airway ◽  
Cl Channels ◽  
Cystic Fibrosis Transmembrane

Cl- channels located in the apical membrane of secretory epithelia play a key role in epithelial fluid and electrolyte transport. Dysfunction of one of these channels, cystic fibrosis transmembrane conductance regulator (CFTR), causes the genetic disease cystic fibrosis (CF). We review here the properties and regulation of the different types of Cl- channels that have been reported in airway and intestinal epithelia. We begin by describing the properties of the CFTR Cl- channel and then use those properties as a point of reference. We focused particularly on the evidence that localizes specific types of Cl- channel to the apical membrane. With that background, we assess the biological function of various Cl- channels in airway and intestinal epithelia.

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