Separation of two Cl- currents in cultured human and murine mesangial cells: Biophysical and pharmacological characteristics of ICl.vol and ICl.Ca

Cristian D. Cipleu, Carlos E. Palant, Kenton M. Sanders, Gregory M. Dick

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Mesangial cells, a combined smooth muscle- and fibroblast-like phenotype, are important regulators of renal function. These cells exist in a region of variable osmolarity and may require Cl- channels for volume regulation. Additionally, Ca2+-activated Cl- channels in these cells may participate in Ca2+-dependent contractile responses to vasoactive agonists. Relatively little, however, is known about mesangial cell Cl- currents (ICl); including the biophysical description and pharmacological characterization. We used whole-cell patch clamp to study ICl in cultured human and SV40-transformed murine mesangial cells. ICl was measured in cells dialyzed and bathed with symmetrical N-methyl-D-glucamine chloride solutions to minimize cation currents. Dialysis with buffers to control intracellular Ca2+ ([Ca2+]i), extracellular solutions of varied osmolarity, and manipulation of the transmembrane Cl- gradient were used to separate two currents: ICl.vol (volume-sensitive), and ICl.Ca (Ca2+-activated). In symmetrical Cl- with low [Ca2+]i, ICl.vol was outwardly rectifying and modulated by osmolarity. ICl.vol demonstrated slight time- and voltage- dependent inactivation. In symmetrical Cl- with elevated [Ca2+]i and hypertonic bath, ICl.Ca was linear, but in asymmetrical Cl- (low [Cl-]i) was outwardly rectifying and demonstrated time- and voltage-dependent activation. Permeability sequences for both ICl.vol and ICl.Ca were I- > Br- > Cl- > F-; however, there were differences in the relative magnitudes. Tamoxifen inhibited ICl.vol more potently than ICl.Ca, whereas niflumic acid inhibited ICl.Ca more potently than ICl.vol. We have separated and characterized two types of ICl in cultured human and murine mesangial cells. ICl.Ca and ICl.vol have different biophysical and pharmacological characteristics. These observations on ICl.Ca and ICl.vol may provide insight into mesangial cell reactivity and volume regulation.

Original languageEnglish
Pages (from-to)426-436
Number of pages11
JournalJournal of Vascular Research
Volume39
Issue number5
DOIs
StatePublished - 17 Oct 2002

Keywords

  • Ca-activated Clchannels
  • Juxtaglomerular apparatus
  • Tubuloglomerular feedback
  • Volume-sensitive Cl channels

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