title: Role of cytochrome P-450 epoxygenase metabolites in EGF signaling in renal proximal tubule.
abstract: Epidermal growth factor (EGF) is a potent epithelial cell mitogen and induces eicosanoid production in many cell types. The present study examined signaling mechanisms for EGF in the renal proximal tubule, where high concentrations of cytochrome P-450 epoxygenase have been reported. In primary cultures of rabbit proximal tubule cells, EGF (30 nM) increased endogenous epoxyeicosatrienoic acid (EET) levels 5.3 +/- 1.4-fold within 10 min (n = 6). In these cells EGF-stimulated [3H]thymidine incorporation was significantly inhibited by the cytochrome P-450 inhibitors ketoconazole or clotrimazole but not by the cyclooxygenase inhibitor indomethacin. In fura 2-loaded proximal tubule cells, EGF caused a concentration-dependent increase in cytosolic Ca2+ concentration ([Ca2+]i), due to Ca2+ influx, which was inhibited by either ketoconazole or SKF-525A but not by indomethacin. Addition of 5,6-EET (0.5 microM) also induced Ca2+ influx in proximal tubule cells, whereas 8,9-11,12-, or 14,15-EET did not. In cells treated with bis(2-amino-5-methylphenoxy)ethane N,N,N',N'-tetraacetic acid tetraacetoxy-methyl ester to chelate [Ca2+]i, EGF-stimulated [3H]thymidine incorporation. These results indicate that EGF increases EET levels in proximal tubule and suggest that 5,6-EET or its metabolites may be a modulator of EGF-induced [Ca2+]i increases and involved in mitogenesis.
mesh_terms: D015126:8,11,14-Eicosatrienoic Acid / Q000031:analogs & derivatives; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000090762:Cytochrome P-450 CYP2J2; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology / Q000502:physiology*; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000502:physiology*; D008938:Mitosis / Q000187:drug effects; D009994:Osmolar Concentration; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D007295:Inositol Phosphates; D004815:Epidermal Growth Factor; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D000090762:Cytochrome P-450 CYP2J2; D015126:8,11,14-Eicosatrienoic Acid; D002118:Calcium