title: Evidence for independent Cl- and HCO3- secretion and involvement of an apical Na(+)-HCO3- cotransporter in cultured rat epididymal epithelia.
abstract: Electrogenic chloride and bicarbonate secretion by cultured rat epididymal epithelia was studied using the short-circuit current (ISC) technique. When incubated in normal solution, 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (cpt-cAMP) caused a rise in the ISC, which was attributable to Cl- and HCO3- secretion. Cl- secretion was found to contribute to the initial transient phase, whereas HCO3- secretion contributed to the sustained phase of the response. HCO3- secretion involves a basolaterally placed Na(+)-H+ exchanger and apical anion channel, most probably the cystic fibrosis transmembrane conductance regulator (CFTR). There is also evidence that an apical electrogenic Na(+)-HCO3- cotransporter is involved in HCO3- exit. CFTR accounted for 70% of HCO3- secretion, while the Na(+)-HCO3- cotransporter accounted for 30%. The possibility that the cotransporter may serve as an alternative pathway for HCO3- secretion in cystic fibrosis is discussed.
authors: Department of Physiology, Chinese University of Hong Kong, Shatin, New Territories, Hong Kong.
authors: H C
authors: HC
authors: Chan
authors: W H
authors: WH
authors: Ko
authors: W
authors: W
authors: Zhao
authors: W O
authors: WO
authors: Fu
authors: P Y
authors: PY
authors: Wong
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000086:Acetazolamide / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002034:Bumetanide / Q000494:pharmacology; D002352:Carrier Proteins / Q000502:physiology; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D003470:Culture Media / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D004594:Electrophysiology; D004822:Epididymis / Q000378:metabolism*; D004848:Epithelium / Q000502:physiology*; D006593:Hexokinase / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013873:Thionucleotides / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D001639:Bicarbonates; D002352:Carrier Proteins; D002712:Chlorides; D003470:Culture Media; D013873:Thionucleotides; D002034:Bumetanide; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000584:Amiloride; D000242:Cyclic AMP; D006593:Hexokinase; D000086:Acetazolamide; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid