Dual actions of the metabolic inhibitor, sodium azide on KATP channel currents in the rat CRI-G1 insulinoma cell line

J Harvey, S C Hardy, M L Ashford

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    Abstract

    1. The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP-sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI-G1) cell line using a combination of whole cell and single channel recording techniques. 2. Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI-G1 cells with a concomitant increase in K+ conductance. This is due to activation of KATP channels as the sulphonylurea tolbutamide (100 µM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 µM) or oligomycin (2 µM) did not hyperpolarize CRI-G1 cells or increase K+ conductance. 3. In cell-attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in KATP channel activity, an action readily reversible by tolbutamide (100 µM). Application of sodium azide (3 mM), in the presence of Mg-ATP, to the intracellular surface of excised inside-out patches also increased KATP channel activity, in a reversible manner. 4. In contrast, rotenone (10 µM) or oligomycin (2 µM) did not increase KATP channel activity in either cell-attached, in the absence of glucose, or inside-out membrane patch recordings. 5. Addition of sodium azide (3 mM) to the intracellular surface of inside-out membrane patches in the presence of Mg-free ATP or the non-hydrolysable analogue 5'-adenylylimidodiphosphate (AMP-PNP) inhibited, rather than increased, KATP channel activity. 6. In conclusion, sodium azide, but not rotenone or oligomycin, directly activates KATP channels in CRI-G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.

    Original languageEnglish
    Pages (from-to)51-60
    Number of pages10
    JournalBritish Journal of Pharmacology
    Volume126
    Issue number1
    DOIs
    Publication statusPublished - Jan 1999

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    KATP Channels
    Sodium Azide
    Insulinoma
    Oligomycins
    Rotenone
    Cell Line
    Adenosine Triphosphate
    Adenylyl Imidodiphosphate
    Tolbutamide
    Azides
    Electron Transport
    Diazoxide
    Glucose
    Membranes
    Insulin-Secreting Cells
    Baths

    Cite this

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    title = "Dual actions of the metabolic inhibitor, sodium azide on KATP channel currents in the rat CRI-G1 insulinoma cell line",
    abstract = "1. The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP-sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI-G1) cell line using a combination of whole cell and single channel recording techniques. 2. Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI-G1 cells with a concomitant increase in K+ conductance. This is due to activation of KATP channels as the sulphonylurea tolbutamide (100 µM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 µM) or oligomycin (2 µM) did not hyperpolarize CRI-G1 cells or increase K+ conductance. 3. In cell-attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in KATP channel activity, an action readily reversible by tolbutamide (100 µM). Application of sodium azide (3 mM), in the presence of Mg-ATP, to the intracellular surface of excised inside-out patches also increased KATP channel activity, in a reversible manner. 4. In contrast, rotenone (10 µM) or oligomycin (2 µM) did not increase KATP channel activity in either cell-attached, in the absence of glucose, or inside-out membrane patch recordings. 5. Addition of sodium azide (3 mM) to the intracellular surface of inside-out membrane patches in the presence of Mg-free ATP or the non-hydrolysable analogue 5'-adenylylimidodiphosphate (AMP-PNP) inhibited, rather than increased, KATP channel activity. 6. In conclusion, sodium azide, but not rotenone or oligomycin, directly activates KATP channels in CRI-G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.",
    author = "J Harvey and Hardy, {S C} and Ashford, {M L}",
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    TY - JOUR

    T1 - Dual actions of the metabolic inhibitor, sodium azide on KATP channel currents in the rat CRI-G1 insulinoma cell line

    AU - Harvey, J

    AU - Hardy, S C

    AU - Ashford, M L

    PY - 1999/1

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    N2 - 1. The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP-sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI-G1) cell line using a combination of whole cell and single channel recording techniques. 2. Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI-G1 cells with a concomitant increase in K+ conductance. This is due to activation of KATP channels as the sulphonylurea tolbutamide (100 µM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 µM) or oligomycin (2 µM) did not hyperpolarize CRI-G1 cells or increase K+ conductance. 3. In cell-attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in KATP channel activity, an action readily reversible by tolbutamide (100 µM). Application of sodium azide (3 mM), in the presence of Mg-ATP, to the intracellular surface of excised inside-out patches also increased KATP channel activity, in a reversible manner. 4. In contrast, rotenone (10 µM) or oligomycin (2 µM) did not increase KATP channel activity in either cell-attached, in the absence of glucose, or inside-out membrane patch recordings. 5. Addition of sodium azide (3 mM) to the intracellular surface of inside-out membrane patches in the presence of Mg-free ATP or the non-hydrolysable analogue 5'-adenylylimidodiphosphate (AMP-PNP) inhibited, rather than increased, KATP channel activity. 6. In conclusion, sodium azide, but not rotenone or oligomycin, directly activates KATP channels in CRI-G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.

    AB - 1. The effects of various inhibitors of the mitochondrial electron transport chain on the activity of ATP-sensitive K+ channels were examined in the Cambridge rat insulinoma G1 (CRI-G1) cell line using a combination of whole cell and single channel recording techniques. 2. Whole cell current clamp recordings, with 5 mM ATP in the pipette, demonstrate that the mitochondrial uncoupler sodium azide (3 mM) rapidly hyperpolarizes CRI-G1 cells with a concomitant increase in K+ conductance. This is due to activation of KATP channels as the sulphonylurea tolbutamide (100 µM) completely reversed the actions of azide. Other inhibitors of the mitochondrial electron transport chain, rotenone (10 µM) or oligomycin (2 µM) did not hyperpolarize CRI-G1 cells or increase K+ conductance. 3. In cell-attached recordings, bath application of 3 mM sodium azide (in the absence of glucose) resulted in a rapid increase in KATP channel activity, an action readily reversible by tolbutamide (100 µM). Application of sodium azide (3 mM), in the presence of Mg-ATP, to the intracellular surface of excised inside-out patches also increased KATP channel activity, in a reversible manner. 4. In contrast, rotenone (10 µM) or oligomycin (2 µM) did not increase KATP channel activity in either cell-attached, in the absence of glucose, or inside-out membrane patch recordings. 5. Addition of sodium azide (3 mM) to the intracellular surface of inside-out membrane patches in the presence of Mg-free ATP or the non-hydrolysable analogue 5'-adenylylimidodiphosphate (AMP-PNP) inhibited, rather than increased, KATP channel activity. 6. In conclusion, sodium azide, but not rotenone or oligomycin, directly activates KATP channels in CRI-G1 insulin secreting cells. This action of azide is similar to that reported previously for diazoxide.

    U2 - 10.1038/sj.bjp.0702267

    DO - 10.1038/sj.bjp.0702267

    M3 - Article

    VL - 126

    SP - 51

    EP - 60

    JO - British Journal of Pharmacology

    JF - British Journal of Pharmacology

    SN - 0007-1188

    IS - 1

    ER -