Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes

Seung Cheol Ahn, Sang Jin Lee, Yong Sook Goo, Jae Hoon Sim, Insuk So, Ki Whan Kim

Research output: Contribution to journalArticleResearchpeer-review

2 Citations (Scopus)

Abstract

The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54±5%) and frequency (60±8%) by 1 μM phorbol 12, 13 dibutyrate (PDBu, n=6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n=5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using β-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96±8%) nor the frequency of these currents was inhibited significantly by 1 μM PDBu (n=5). Like PDBu, 5 μM 2-{2-[4-(4-nitrobenzyloxy)phenyl]ethyl} isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45±6%) and frequency (26±2%) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.

Original languageEnglish
Pages (from-to)417-424
Number of pages8
JournalPflugers Archiv European Journal of Physiology
Volume441
Issue number4
DOIs
StatePublished - 19 Feb 2001

Fingerprint

Muscle Cells
Protein Kinase C
Stomach
Guinea Pigs
Modulation
Clamping devices
Patch-Clamp Techniques
Escin
Phorbol 12,13-Dibutyrate
Tromethamine
Electric potential
2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate

Keywords

  • Gastric myocytes
  • Guinea-pig
  • Na/Ca exchanger
  • Protein kinase C
  • STOCs

Cite this

@article{7b93731774684988b9a5de1c7bb4243f,
title = "Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes",
abstract = "The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54±5{\%}) and frequency (60±8{\%}) by 1 μM phorbol 12, 13 dibutyrate (PDBu, n=6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n=5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using β-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96±8{\%}) nor the frequency of these currents was inhibited significantly by 1 μM PDBu (n=5). Like PDBu, 5 μM 2-{2-[4-(4-nitrobenzyloxy)phenyl]ethyl} isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45±6{\%}) and frequency (26±2{\%}) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.",
keywords = "Gastric myocytes, Guinea-pig, Na/Ca exchanger, Protein kinase C, STOCs",
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Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes. / Ahn, Seung Cheol; Lee, Sang Jin; Goo, Yong Sook; Sim, Jae Hoon; So, Insuk; Kim, Ki Whan.

In: Pflugers Archiv European Journal of Physiology, Vol. 441, No. 4, 19.02.2001, p. 417-424.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes

AU - Ahn, Seung Cheol

AU - Lee, Sang Jin

AU - Goo, Yong Sook

AU - Sim, Jae Hoon

AU - So, Insuk

AU - Kim, Ki Whan

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N2 - The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54±5%) and frequency (60±8%) by 1 μM phorbol 12, 13 dibutyrate (PDBu, n=6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n=5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using β-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96±8%) nor the frequency of these currents was inhibited significantly by 1 μM PDBu (n=5). Like PDBu, 5 μM 2-{2-[4-(4-nitrobenzyloxy)phenyl]ethyl} isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45±6%) and frequency (26±2%) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.

AB - The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54±5%) and frequency (60±8%) by 1 μM phorbol 12, 13 dibutyrate (PDBu, n=6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n=5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using β-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96±8%) nor the frequency of these currents was inhibited significantly by 1 μM PDBu (n=5). Like PDBu, 5 μM 2-{2-[4-(4-nitrobenzyloxy)phenyl]ethyl} isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45±6%) and frequency (26±2%) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.

KW - Gastric myocytes

KW - Guinea-pig

KW - Na/Ca exchanger

KW - Protein kinase C

KW - STOCs

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DO - 10.1007/s004240000446

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