title: Role of Ca2+/CaMK II in Ca(2+)-induced K+ channel inhibition in rat CCD principal cell.
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.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut 06520.
authors.forename: M
authors.initials: M
authors.lastname: Kubokawa
authors.forename: W
authors.initials: W
authors.lastname: Wang
authors.forename: C M
authors.initials: CM
authors.lastname: McNicholas
authors.forename: G
authors.initials: G
authors.lastname: Giebisch
mesh_terms: D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000031:analogs & derivatives*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D007211:Indoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000502:physiology*; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D007211:Indoles; D007546:Isoquinolines; D008301:Maleimides; D010879:Piperazines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C063302:KN 62; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C070515:bisindolylmaleimide I; D002118:Calcium