Role of Ca2+/CaMK II in Ca2+-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 Ca 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 Ca /calmodulin-dependent protein kinase II (CaMK II) in mediating the Ca -induced inhibitory effect. In cell- attached patches of principal cells of rat tubules, clamping of intracellular Ca concentration at 400 nM by using 1 μM 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 Ca on K channel activity (83.2 and 50.7% of the control value, respectively). Even in the presence of KN-62, addition of 10 μM PMA significantly decreased channel activity to 57.2% of the control value. The Ca -induced inhibition was completely abolished by simultaneous incubation with both KN-62 and GF-109203X. In inside-out patches, addition of 20 μg/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 -induced inhibition of the activity of the apical K channel of rat CCD. + 2+ 2+ 2+ 2+ 2+ + 2+ 2+ +
  • Digital Object Identifier (doi)

    Author List

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

  • 268
  • Issue

  • 2 37-2