Cftr mediates electrogenic chloride secretion in mouse inner medullary collecting duct (mimcd-k2) cells. Vandorpe, David, Neil Kizer, Flora Ciampollilo-Bates, Bryan Moyer, Katherine Karlson, William B. Guggino, and Bruce A. Stanton. Department of Physiology, Dartmouth Medical School, Hanover, NH, 03755 and Department of Physiology, Johns Hopkins University. Baltimore, MD, 21205
APStracts 2:0171C, 1995.
Previously, we demonstrated that the inner medullary collecting duct cell line mIMCD-K2 secretes chloride (Cl-) by an electrogenic mechanism (15,16). The goal of the present study was to characterize the Cl- channel responsible for cAMP-stimulated Cl- secretion. To this end we measured Cl- currents using the patch clamp technique. In whole cell patch clamp experiments, 8-(4-chlorophenylthio)-cAMP (CPT -cAMP) activated Cl- currents that were time and voltage-independent, inhibited by diphenylamine 2-carboxylate (DPC), and had a linear 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 (NPPB) and glibenclamide blocked the 7 pS Cl- channel, whereas 4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) was ineffective. By RT-PCR we isolated a partial cDNA clone encoding the cystic fibrosis transmembrane conductance regulator (CFTR) in mIMCD-K2 cells. We conclude that cAMP stimulates electrogenic Cl- secretion in IMCD cells by activating CFTR Cl- channels. 

Received 21 December 1994; accepted in final form 11 April 1995.
APS Manuscript Number C734-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.