Ca2+ and cAMP-activated Cl- conductances mediate Cl- secretion in a mouse renal inner medullary collecting duct cell line

J Physiol. 2000 Mar 1;523 Pt 2(Pt 2):325-38. doi: 10.1111/j.1469-7793.2000.t01-1-00325.x.


1. The nature of Cl- conductance(s) participating in transepithelial anion secretion by renal inner medullary collecting duct (IMCD, mIMCD-K2 cell line) was investigated. 2. Extracellular ATP (100 microM) stimulated a transient increase in both whole-cell Cl- conductance and intracellular free Ca2+. In contrast, ionomycin (10-100 nM) caused a sustained increase in whole-cell Cl- conductance. Pre-loading cells with the Ca2+ buffer BAPTA abolished the ATP-dependent responses and delayed the onset of the increase observed with ionomycin. 3. The Ca2+-activated whole-cell Cl- current stimulated by ATP (peak) and ionomycin (maximal) displayed (i) a linear steady-state current-voltage relationship and (ii) time and voltage dependence with slow activation at +80 mV and slow inactivation at -80 mV. In BAPTA-loaded cells, ionomycin-elicited whole-cell currents exhibited pronounced outward rectification with time-dependent activation/inactivation. 4. Ca2+-activated and forskolin-activated Cl- conductances co-exist since ATP activation of whole-cell current occurred during a maximal stimulation by forskolin in single cell recordings. 5. In IMCD epithelial layers, ATP and ionomycin stimulated an inward short circuit current (Isc) dependent upon basal medium Na+ and Cl-/HCO3- but independent of the presence of apical bathing medium Na+ and Cl-/HCO3-. This was identical to forskolin stimulation and consistent with transepithelial anion secretion. 6. PCR amplification of reverse-transcribed mRNA using gene-specific primers demonstrated expression of both cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and Ca2+-activated Cl- channel (mCLCA1) mRNA in mIMCD-K2 cells. 7. Ca2+ and forskolin-activated Cl- conductances participate in anion secretion by IMCD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Adenosine Triphosphate / pharmacology
  • Animals
  • Biological Transport, Active / drug effects
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Cell Line
  • Chloride Channels / biosynthesis
  • Chloride Channels / drug effects
  • Chloride Channels / genetics
  • Chloride Channels / metabolism*
  • Chlorides / metabolism*
  • Colforsin / pharmacology
  • Cyclic AMP / metabolism*
  • Cyclic AMP / pharmacology
  • Cystic Fibrosis Transmembrane Conductance Regulator / biosynthesis
  • Cystic Fibrosis Transmembrane Conductance Regulator / genetics
  • Egtazic Acid / analogs & derivatives
  • Egtazic Acid / pharmacology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Indicators and Reagents / pharmacology
  • Intracellular Fluid / metabolism
  • Ion Transport / drug effects
  • Ionomycin / pharmacology
  • Ionophores / pharmacology
  • Kidney Tubules, Collecting / drug effects
  • Kidney Tubules, Collecting / metabolism*
  • Mice
  • Patch-Clamp Techniques
  • RNA, Messenger / biosynthesis


  • Chloride Channels
  • Chlorides
  • Clca3a1 protein, mouse
  • Indicators and Reagents
  • Ionophores
  • RNA, Messenger
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Colforsin
  • Egtazic Acid
  • Ionomycin
  • Adenosine Triphosphate
  • Cyclic AMP
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium