title: alpha1-adrenoceptor agonists and IGF-1, myocardial hypertrophic factors, regulate the Kv1.5 K+ channel expression differentially in cultured newborn rat ventricular cells.
abstract: Interest has arisen concerning the importance of alpha-adrenergic function and insulin-like growth factor-1 (IGF-1) in cardiac remodelling. The hypothesis that these two factors may underlie the regulation of voltage-gated K+ channel expression in hypertrophied cardiomyocytes was tested by performing Western blot analysis of the Kv1.5 K+ channel alpha-subunit in cultured newborn rat ventricular cells. Myocyte size was quantified by surface area and total cell protein concentration. Cell exposure to the alpha1-adrenoceptor agonist phenylephrine (PE, 20 microM) and IGF-1 (60 ng/ml) for 72 h both induced a significant increase of cell size indicating myocyte hypertrophy, which could be separately blocked by the protein kinase C inhibitor staurosporine (20 nM) and the tyrosine kinase inhibitor genistein (15 microM). Western blots of cell proteins prepared from myocyte cultures showed a single protein band at 75 kD recognized by the anti-Kv1.5 antibody, and demonstrated a 56% reduction in the Kv1. 5 immunoreactive protein level in the PE-treated cell preparations. This suppression was not affected by staurosporine, but was remarkably attenuated by W7 (20 microM), a selective calmodulin antagonist. In contrast to PE, a 48% enhancement of the protein expression of Kv1.5 channel was induced by IGF-1 and this stimulation was specifically blocked by genistein. Our findings suggest that the differential regulation of cardiac Kv1.5 K+ channel expression can be produced by alpha1-adrenoceptor activation and IGF-1 via distinctive signalling pathways. Calmodulin-dependent kinase and tyrosine kinase contribute importantly to the alpha1-adrenoceptor-mediated decrease and the IGF-1-mediated increase in cardiac Kv1.5 K+ channel expression, respectively.
authors.affiliation: Department of Circulation, Division of Regulation of Organ Function, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-01, Japan.
authors.forename: W
authors.initials: W
authors.lastname: Guo
authors.forename: K
authors.initials: K
authors.lastname: Kamiya
authors.forename: K
authors.initials: K
authors.lastname: Yasui
authors.forename: I
authors.initials: I
authors.lastname: Kodama
authors.forename: J
authors.initials: J
authors.lastname: Toyama
mesh_terms: D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D006352:Heart Ventricles / Q000737:chemistry; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009206:Myocardium / Q000737:chemistry*; D010656:Phenylephrine / Q000494:pharmacology; D015221:Potassium Channels / Q000032:analysis*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D051381:Rats; D017208:Rats, Wistar; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D002147:Calmodulin; D004791:Enzyme Inhibitors; D015221:Potassium Channels; D013449:Sulfonamides; D010656:Phenylephrine; C017967:W 7; D007334:Insulin-Like Growth Factor I; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D019311:Staurosporine