title: Activation of extracellular-signal regulated kinase by epidermal growth factor is potentiated by cAMP-elevating agents in primary cultures of adult rat hepatocytes.
abstract: We investigated the effects of α- and β-adrenergic agonists on epidermal growth factor (EGF)-stimulated extracellular-signal regulated kinase (ERK) isoforms in primary cultures of adult rat hepatocytes. Hepatocytes were isolated and cultured with EGF (20 ng/ml) and/or α(1)-, α(2)- and β(2)-adrenergic agonists. Phosphorylated ERK isoforms (ERK1; p44 mitogen-activated protein kinase (MAPK) and ERK2; p42 MAPK) were detected by Western blotting analysis using anti-phospho-ERK1/2 antibody. The results show that EGF induced a 2.5-fold increase in ERK2-, but not ERK1-, phosphorylation within 3 min. This EGF-induced ERK2 activation was abolished by treatment with the EGF-receptor kinase inhibitor AG1478 (10(-7) M) or the MEK (MAPK kinase) inhibitor PD98059 (10(-6) M). The α(2)-adrenergic and β(2)-adrenergic agonists, UK14304 (10(-6) M) and metaproterenol (10(-6) M), respectively, had no effect in the absence of EGF, but metaproterenol significantly potentiated EGF-induced ERK2 phosphorylation. Moreover, the cell-permeable cAMP analog 8-bromo cAMP (10(-7) M), also potentiated EGF-induced ERK2 phosphorylation. The effects of these analogs were antagonized by the protein kinase A (PKA) inhibitor H-89 (10(-7) M). These results suggest that direct or indirect activation of PKA represents a positive regulatory mechanism for EGF stimulation of ERK2 induction.
authors.affiliation: Department of Clinical Pharmacology, Faculty of Pharmaceutical Sciences, Josai University, Sakado, Saitama 350–02, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Moteki
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Kimura
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ogihara
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D058647:Adrenergic alpha-2 Receptor Agonists / Q000494:pharmacology; D058666:Adrenergic beta-2 Receptor Agonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D018929:Cell Culture Techniques; D049109:Cell Proliferation / Q000187:drug effects; D000242:Cyclic AMP / Q000819:agonists* / Q000031:analogs & derivatives; D004353:Drug Evaluation, Preclinical; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000502:physiology; D048370:MAP Kinase Kinase 2 / Q000032:analysis; D008297:Male; D009921:Metaproterenol / Q000494:pharmacology; D048052:Mitogen-Activated Protein Kinase 3 / Q000032:analysis; D058990:Molecular Targeted Therapy; D010766:Phosphorylation; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D058666:Adrenergic beta-2 Receptor Agonists; D011810:Quinoxalines; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000068438:Brimonidine Tartrate; D009921:Metaproterenol; D004815:Epidermal Growth Factor; D000242:Cyclic AMP; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D048052:Mitogen-Activated Protein Kinase 3; D048370:MAP Kinase Kinase 2