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Chloride Secretion in Kidney Distal Epithelial Cells (A6) Evoked by Cadmium

Authors
Journal
Toxicology and Applied Pharmacology
0041-008X
Publisher
Elsevier
Publication Date
Volume
163
Issue
3
Identifiers
DOI: 10.1006/taap.1999.8852
Keywords
  • Cadmium
  • Calcium
  • Chloride-Channel Blockers
  • Chloride Secretion
  • Fluorescence
  • Heavy Metals
  • Renal Epithelial Cells (A6)
  • Short-Circuit-Current
  • 6-Methoxy-N-(Sulfopropyl)Quinolinium (Spq)

Abstract

Abstract The effect of Cd 2+ on chloride secretion was examined in A6 renal epithelia cells by chloride-sensitive fluorescence (SPQ probe) and by the short-circuit-current (I sc) technique. Depleting the cells of Cl − suggests that the Cd 2+-activated I sc (ΔI sc(Cd)) is dependent on the presence of Cl − ions. Among the Cl −-channel inhibitors the fenemates, flufenamic acid (FFA) and niflumic acid (NFA), and 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) significantly lowered ΔI sc(Cd) compared with control level. In SPQ-loaded A6 cells, Cd 2+ evoked an increase in Cl − secretion ([ΔCl −] Cd), which significantly exceeded the basal Cl − transport and was blockable by FFA and NFA. The closely related metals, Zn 2+ or Ni 2+, were also able to activate Cl − secretion. Preexposure of Zn 2+ or Ni 2+ completely prevented [ΔCl −] Cd, suggesting that Zn 2+ and Ni 2+ probably use similar mechanisms. Like Cd 2+, thapsigargin (TG), an inhibitor of intracellular Ca 2+-ATPase and the Ca 2+-ionophore A23187, induced an increase in I sc. Moreover, TG and Cd 2+ were able to neutralize the responses of the counterparts as also observed in I sc measurements, which indicates that Cd 2+ activates Cl − secretion in a Ca 2+-dependent manner. Hence, this study supports the idea that basolateral Cd 2+ (possibly also Zn 2+ and Ni 2+), probably through a Ca 2+-sensing receptor, causes calcium mobilization that activates apical fenemate-sensitive chloride channels leading to chloride secretion in A6 cells.

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