Effect of englitazone on KATP and calcium-activated non-selective cation channels in CRI-G1 insulin-secreting cells

I. C. M. Rowe, Kevin Lee, R N Khan, M L Ashford

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)

    Abstract

    1. The effects of englitazone sodium, an antidiabetic agent, on ion channel activity in the CRI-G1 insulin secreting cell line was examined by use of the patch clamp technique. 2. Application of englitazone to the outside of CRI-G1 cells in the whole-cell recording configuration produced concentration-dependent inhibition of KATP currents with an IC50 value of 8 microM. The inhibition of the K+ current was not affected by the removal of Mg2+ ions from or the addition of trypsin to the solution bathing the intracellular surface of the cell membrane. 3. Englitazone also inhibited KATP channel activity in recordings from inside out excise membrane patches. The concentration-dependence of inhibition was identical to that observed in whole-cell recordings and was voltage-independent. Single channel recordings confirmed that neither the absence or presence of Mg2+ ions nor the addition of trypsin at the intracellular surface of the membrane influenced the inhibition of KATP channels by englitazone. 4. Englitazone also inhibited Ca(2+)-activated non-selective cation (NSCa) channels in inside-out patches in a concentration-dependent and voltage-independent manner with an IC50 value of 10 microM. In comparison, the non-sulphonylurea KATP channel blocker ciclazindol produced a slight voltage-dependent inhibition of the NSCa channel at a concentration of 20 microM. 5. In whole-cell recordings englitazone, at a relatively high concentration (50 microM) in comparison with that required to block KATP and NSCa channels, inhibited voltage-activated Ca2+ currents by 33% but did not inhibit voltage-activated K+ and Na+ currents. 6. It is concluded that englitazone is a novel blocker of NSCa and KATP channels. The inhibition of KATP channels occurs following procedures that dissociate sulphonylurea receptor coupling to the channel. The equipotent and voltage-independent inhibition of NSCa and KATP channels by englitazone may indicate a common mechanism of block.
    Original languageEnglish
    Pages (from-to)531-9
    Number of pages9
    JournalBritish Journal of Pharmacology
    Volume121
    Issue number3
    DOIs
    Publication statusPublished - Jun 1997

    Keywords

    • Rats
    • Animals
    • Hypoglycemic Agents
    • Calcium
    • Benzopyrans
    • Thiazoles
    • Thiazolidinediones
    • Ion Channels
    • Adenosine Triphosphate
    • Potassium Channels
    • Insulin
    • Cell Line

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