Extracellular zinc stimulates a calcium-activated chloride conductance through mobilisation of intracellular calcium in renal inner medullary collecting duct cells.
We have used the perforated patch clamp and fura-2 fluorescence techniques to study the effect of extracellular Zn(2+) on whole-cell Ca(2+)-activated Cl(-) currents (I (CLCA)) in mouse inner medullary collecting duct cells (mIMCD-3). I (CLCA) was spontaneously active in 74% of cells under basal conditions and displayed time and voltage-independent kinetics and an outwardly rectifying current/voltage relationship (I/V). Addition of zinc chloride (10-400 microM) to the bathing solution resulted in a dose-dependent increase in I (CLCA) with little change in Cl(-) selectivity or biophysical characteristics, whereas gadolinium chloride (30 microM) and lanthanum chloride (100 microM) had no significant effect on the whole-cell current. Using fura-2-loaded mIMCD-3 cells, extracellular Zn(2+) (400 microM) stimulated an increase in intracellular Ca(2+) to an elevated plateau. The Zn(2+)-stimulated [Ca(2+)](i) increase was inhibited by thapsigargin (200 nM), the IP(3) receptor antagonist 2-aminoethoxydiphenyl borate (10 microM) and removal of bath Ca(2+). Pre-exposure to Zn(2+) (400 microM) markedly attenuated the ATP (100 microM)-stimulated [Ca(2+)](i) increase. These data are consistent with the hypothesis that extracellular Zn(2+) stimulates an increase in [Ca(2+)](i) by a release of calcium from thapsigargin/IP(3) sensitive stores. A possible physiological role for a divalent metal ion receptor, distinct from the extracellular Ca(2+)-sensing receptor, in IMCD cells is discussed.
Linley
J E
JE
Institute of Cell and Molecular Biosciences, University Medical School, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
Simmons
N L
NL
Gray
M A
MA
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism / Q000502:physiology*; D002712:Chlorides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005470:Fluorometry; D007679:Kidney Medulla / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018408:Patch-Clamp Techniques; D019284:Thapsigargin / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology*; D017967:Zinc Compounds / Q000494:pharmacology
D001896:Boron Compounds; D018118:Chloride Channels; D002712:Chlorides; D017967:Zinc Compounds; D019284:Thapsigargin; C016837:zinc chloride; C109986:2-aminoethoxydiphenyl borate; D015032:Zinc; D002118:Calcium