Large Ca 2+ -activated K + channels responsive to angiotensin II in cultured human mesangial cells

J. D. Stockand, Steven Claude Sansom

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Abstract

The patch-clamp method was used to determine the properties and response to angiotensin II (ANG II) of K + channels in subpassages of human mesangial cell cultures. In cell-attached patches, with 140 mM KCl in the bath and cell potential equal to 40 mV, the open probability (P(o)) of large K + channels (MK(Ca)) was 0.8 with 0.5 mM Ca 2+ in the bath and < 0.05 if the bath Ca 2+ concentration was reduced to 1.0 μM. Open and closed dwell-time histograms of MK(Ca) displayed both fast and slow time constants. Addition of ANG II (100 nM) to the bath solution (Ca 2+ = 1.0 μM) increased the P(o) of MK(Ca) in cyclic bursts by decreasing the time constant of the slow closed state. In excised inside-out patches, the mean single-channel conductance of MK(Ca) was 206 pS in symmetrical 140 mM KCl. The selectivity sequence, established in asymmetrical cationic solutions, was K + (1.0) > Rb + (0.54) > NH 4 / + (0.11) > > Cs + = Na + (<0.05). The P(o) of MK(Ca) was increased by depolarizing potentials and high bath Ca 2+ . The Boltzmann distribution was consistent with an effective valence of 1.0, and the Hill coefficient for Ca 2+ activation was 0.52. We conclude that MK(Ca) has properties similar to large Ca 2+ -activated K + channels and may act to repolarize the membrane of mesangial cells in response to an agonist-induced mobilization of intracellular Ca 2+ .

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume267
Issue number4 37-4
StatePublished - Nov 8 1994

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Mesangial Cells
Baths
Angiotensin II
Cell Culture Techniques
Membranes

Keywords

  • mesangium
  • patch clamp
  • potassium

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

Cite this

@article{405d3bb0bd854e399113f097ed163663,
title = "Large Ca 2+ -activated K + channels responsive to angiotensin II in cultured human mesangial cells",
abstract = "The patch-clamp method was used to determine the properties and response to angiotensin II (ANG II) of K + channels in subpassages of human mesangial cell cultures. In cell-attached patches, with 140 mM KCl in the bath and cell potential equal to 40 mV, the open probability (P(o)) of large K + channels (MK(Ca)) was 0.8 with 0.5 mM Ca 2+ in the bath and < 0.05 if the bath Ca 2+ concentration was reduced to 1.0 μM. Open and closed dwell-time histograms of MK(Ca) displayed both fast and slow time constants. Addition of ANG II (100 nM) to the bath solution (Ca 2+ = 1.0 μM) increased the P(o) of MK(Ca) in cyclic bursts by decreasing the time constant of the slow closed state. In excised inside-out patches, the mean single-channel conductance of MK(Ca) was 206 pS in symmetrical 140 mM KCl. The selectivity sequence, established in asymmetrical cationic solutions, was K + (1.0) > Rb + (0.54) > NH 4 / + (0.11) > > Cs + = Na + (<0.05). The P(o) of MK(Ca) was increased by depolarizing potentials and high bath Ca 2+ . The Boltzmann distribution was consistent with an effective valence of 1.0, and the Hill coefficient for Ca 2+ activation was 0.52. We conclude that MK(Ca) has properties similar to large Ca 2+ -activated K + channels and may act to repolarize the membrane of mesangial cells in response to an agonist-induced mobilization of intracellular Ca 2+ .",
keywords = "mesangium, patch clamp, potassium",
author = "Stockand, {J. D.} and Sansom, {Steven Claude}",
year = "1994",
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T1 - Large Ca 2+ -activated K + channels responsive to angiotensin II in cultured human mesangial cells

AU - Stockand, J. D.

AU - Sansom, Steven Claude

PY - 1994/11/8

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N2 - The patch-clamp method was used to determine the properties and response to angiotensin II (ANG II) of K + channels in subpassages of human mesangial cell cultures. In cell-attached patches, with 140 mM KCl in the bath and cell potential equal to 40 mV, the open probability (P(o)) of large K + channels (MK(Ca)) was 0.8 with 0.5 mM Ca 2+ in the bath and < 0.05 if the bath Ca 2+ concentration was reduced to 1.0 μM. Open and closed dwell-time histograms of MK(Ca) displayed both fast and slow time constants. Addition of ANG II (100 nM) to the bath solution (Ca 2+ = 1.0 μM) increased the P(o) of MK(Ca) in cyclic bursts by decreasing the time constant of the slow closed state. In excised inside-out patches, the mean single-channel conductance of MK(Ca) was 206 pS in symmetrical 140 mM KCl. The selectivity sequence, established in asymmetrical cationic solutions, was K + (1.0) > Rb + (0.54) > NH 4 / + (0.11) > > Cs + = Na + (<0.05). The P(o) of MK(Ca) was increased by depolarizing potentials and high bath Ca 2+ . The Boltzmann distribution was consistent with an effective valence of 1.0, and the Hill coefficient for Ca 2+ activation was 0.52. We conclude that MK(Ca) has properties similar to large Ca 2+ -activated K + channels and may act to repolarize the membrane of mesangial cells in response to an agonist-induced mobilization of intracellular Ca 2+ .

AB - The patch-clamp method was used to determine the properties and response to angiotensin II (ANG II) of K + channels in subpassages of human mesangial cell cultures. In cell-attached patches, with 140 mM KCl in the bath and cell potential equal to 40 mV, the open probability (P(o)) of large K + channels (MK(Ca)) was 0.8 with 0.5 mM Ca 2+ in the bath and < 0.05 if the bath Ca 2+ concentration was reduced to 1.0 μM. Open and closed dwell-time histograms of MK(Ca) displayed both fast and slow time constants. Addition of ANG II (100 nM) to the bath solution (Ca 2+ = 1.0 μM) increased the P(o) of MK(Ca) in cyclic bursts by decreasing the time constant of the slow closed state. In excised inside-out patches, the mean single-channel conductance of MK(Ca) was 206 pS in symmetrical 140 mM KCl. The selectivity sequence, established in asymmetrical cationic solutions, was K + (1.0) > Rb + (0.54) > NH 4 / + (0.11) > > Cs + = Na + (<0.05). The P(o) of MK(Ca) was increased by depolarizing potentials and high bath Ca 2+ . The Boltzmann distribution was consistent with an effective valence of 1.0, and the Hill coefficient for Ca 2+ activation was 0.52. We conclude that MK(Ca) has properties similar to large Ca 2+ -activated K + channels and may act to repolarize the membrane of mesangial cells in response to an agonist-induced mobilization of intracellular Ca 2+ .

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