Expression of calcium channel subunits in the normal and diseased human myocardium |
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Authors: | H. Hasse A. Kresse A. Hohaus H. D. Schulte M. Maier K. J. Osterziel P. E. Lange I. Morano |
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Affiliation: | (1) Max-Delbrück Center for Molecular Medicine, Robert-Rössle Strasse 10, D-13125 Berlin, Germany;(2) Department of Thoracic Cardiovascular Surgery, Heinrich-Heine University, Düsseldorf, Germany;(3) German Heart Center, Berlin, Germany;(4) Franz-Volhard Klinik, Humboldt University, Berlin, Germany |
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Abstract: | We investigated the expression of 1 and subunits of the L-type Ca2+ channel on the protein level in cardiac preparations from normal human heart ventricles and from the hypertrophied septum of patients with hypertrophic obstructive cardiomyopathy (HOCM). 1,4-Dihydropyridine (DHP) binding and immunorecognition by polyclonal antibodies directed against the C-terminal amino acid sequences of the 2 and 3 subunits were used for detection and quantification of 1, 2, and 3 subunits. Bmax of high-affinity DHP binding was 35±2 fmol/mg protein in HOCM and 20±2 fmol/mg protein in normal human hearts (P<0.05). In rabbit hearts the anti-2 subunit antibody immunoprecipitated 80% of the total amount of DHP-labeled Ca2+ channels present in the assay. Under identical experimental conditions 25% of labeled Ca2+ channels were recovered in the immunoprecipitates of both normal and HOCM ventricles. A similar partial immunoprecipitation was observed in pig hearts. Immunoblot analysis demonstrated that the 2 subunit was associated with the DHP receptor/Ca2+ channel in cardiac muscle of rabbit, pig, and human heart. In neither of these purified cardiac Ca2+ channels was the 3 subunit isoform detected. Our results suggest that both 1 and 2 subunit expression is upregulated in HOCM in a coordinate manner.Abbreviations Bmax Maximal number of binding sites - DHP 1,4-Dihydropyridine - HOCM Hypertrophic obstructive cardiomyopathy - NH Normal human heart |
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Keywords: | L-type calcium channel /content/nn1061nl8q863780/xxlarge946.gif" alt=" beta" align=" MIDDLE" BORDER=" 0" > Subunit isoforms Human heart Cardiac hypertrophy |
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