title: IGF-I and bFGF differentially influence atrial natriuretic factor and alpha-smooth muscle actin expression in cultured atrial compared to ventricular adult rat cardiomyocytes.
abstract: In the present study, we compare expression, storage and secretion of the atrial natriuretic factor (ANF) in atrial and ventricular adult rat cardiomyocytes (aARC and vARC) in long-term culture. The influence of insulin-like growth factor-I (IGF-I) and of basic fibroblast growth factor (bFGF) on ANF production and secretion, as well as on the expression of a structural component, alpha-smooth muscle actin (alpha-sm actin), was studied in the two cell types. Antibodies against alpha-ANF were used for immunocytochemical localization of ANF. aARC contained more ANF-granules than vARC, and they were distributed throughout the cell bodies. Quantitative determination of ANF storage and secretion was done by radioimmunoassay (RIA; 125I), and it was demonstrated that aARC stored and secreted ANF 18- and 16-times more, respectively, when compared to vARC. Immuno-electron microscopy confirmed that ANF storing secretory granules were present in both types of cardiomyocytes. Expression of ANF and alpha-sm actin in aARC and vARC responded differently to treatment with either IGF-I or bFGF. In aARC, neither IGF-I nor bFGF had an influence on expression of ANF. In vARC, expression of ANF was downregulated by IGF-I and upregulated by bFGF with regard to both immunoreactivity and message. In contrast to vARC, expression of alpha-sm actin was not affected by IGF-I in aARC, whereas bFGF produced a strong upregulation similar to that found in vARC. Mitogen-activated protein kinases (MAPK) 42 and 44, though, were equally activated by bFGF and IGF-I in both aARC and vARC.
authors.affiliation: Institute of Cell Biology, Swiss Federal Institute of Technology, CH-8093 Zürich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Eppenberger-Eberhardt
authors.forename: S
authors.initials: S
authors.lastname: Aigner
authors.forename: M Y
authors.initials: MY
authors.lastname: Donath
authors.forename: V
authors.initials: V
authors.lastname: Kurer
authors.forename: P
authors.initials: P
authors.lastname: Walther
authors.forename: C
authors.initials: C
authors.lastname: Zuppinger
authors.forename: M C
authors.initials: MC
authors.lastname: Schaub
authors.forename: H M
authors.initials: HM
authors.lastname: Eppenberger
mesh_terms: D000199:Actins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000096:biosynthesis* / Q000235:genetics; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006325:Heart Atria / Q000166:cytology / Q000187:drug effects*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects*; D006984:Hypertrophy; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009928:Organ Specificity; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000199:Actins; C472610:atrial natriuretic peptide, rat; D016222:Fibroblast Growth Factor 2; D007334:Insulin-Like Growth Factor I; D009320:Atrial Natriuretic Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases