Role of Ca2+/CaMK II in Ca(2+)-induced K+ channel inhibition in rat CCD principal cell.

Academic Article

Abstract

  • The apical low-conductance K+ channel of rat cortical collecting duct (CCD) is inhibited by increased intracellular Ca2+ concentrations. This effect has been shown to be mediated at least in part by activation of protein kinase C (PKC). In the present study, we used the patch-clamp technique to examine the role of Ca2+/calmodulin-dependent protein kinase II (CaMK II) in mediating the Ca(2+)-induced inhibitory effect. In cell-attached patches of principal cells of rat tubules, clamping of intracellular Ca2+ concentration at 400 nM by using 1 microM ionomycin reduced channel activity to 26.5% of the control value. A further reduction in channel activity, to 8.8% of the control value, was observed following the addition of phorbol 12-myristate 13-acetate (PMA), an agent known to activate PKC. Pretreatment of cells with KN-62 (CaMK II inhibitor) or GF-109203X (PKC inhibitor) attenuated the inhibitory effect of Ca2+ on K+ channel activity (83.2 and 50.7% of the control value, respectively). Even in the presence of KN-62, addition of 10 microM PMA significantly decreased channel activity to 57.2% of the control value. The Ca(2+)-induced inhibition was completely abolished by simultaneous incubation with both KN-62 and GF-109203X. In inside-out patches, addition of 20 micrograms/ml CaMK II in the presence of a PKC inhibitor reduced channel activity to 66.2% of control values. It is concluded that CaMK II is involved in mediating the Ca(2+)-induced inhibition of the activity of the apical K+ channel of rat CCD.

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    Keywords

  • 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine, Animals, Calcium, Calcium-Calmodulin-Dependent Protein Kinases, Electrophysiology, Female, Indoles, Isoquinolines, Kidney Cortex, Kidney Tubules, Collecting, Male, Maleimides, Piperazines, Potassium Channel Blockers, Potassium Channels, Protein Kinase C, Rats, Rats, Sprague-Dawley

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    Author List

  • Kubokawa M; Wang W; McNicholas CM; Giebisch G

    • Start Page

  • F211

    • End Page

  • F219

    • Volume

  • 268

    • Issue

  • 2 Pt 2