title: Cell-density-dependent expression of the alpha(2)-adrenergic response by epidermal growth factor (EGF) in primary cultures of adult rat hepatocytes.
abstract: Effects of epidermal growth factor (EGF) on the expression of alpha(2)-adrenergic responses were examined in primary cultures of adult rat hepatocytes. The alpha(2)-responses were assessed by the inhibition of the rate of forskolin-stimulated cAMP formation by the selective alpha(2)-adrenergic agonists, oxymetazoline and UK-14304. Hepatocytes cultured with EGF (20 ng/ml) at a high cell density (1.0 x 10(5)/cm2) showed almost no response to the alpha(2)-adrenergic agonists, oxymetazoline and UK-14304 (1-100 mu M). In contrast, when cultured at a low cell density (3.3 x 10(4) cells/cm2) with EGF, forskolin-stimulated cAMP production was inhibited by oxymetazoline and UK-14304 in a dose-dependent manner. The alpha(2)-response was blocked by the alpha2-antagonist yohimbine (10 mu M). It was also reversed by treatment of hepatocytes with pertussis toxin (100 ng/ml). In addition, the effects of EGF on the appearance of alpha(2)-responses were almost completely inhibited by treatment of the hepatocytes with genistein (10 mu M) or cytochalasin B (10 mu M). The alpha(2)-response was abolished when cycloheximide (5 mu M) was added to the cultures. These results demonstrate that when cultured at a low cell density with EGF, adult rat hepatocytes acquire a significant alpha(2)-adrenergic response. The expression of this alpha(2)-response is associated with de novo protein synthesis.
authors.affiliation: Biochemical Pharmacology Group, Faculty of Pharmaceutical Sciences, Josai University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Ogihara
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D002452:Cell Count; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003571:Cytochalasin B / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D008099:Liver / Q000378:metabolism*; D008297:Male; D010109:Oxymetazoline / Q000494:pharmacology; D037342:Pertussis Toxin; D014176:Protein Biosynthesis; D011506:Proteins / Q000187:drug effects; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D007529:Isoflavones; D011506:Proteins; D011810:Quinoxalines; D011942:Receptors, Adrenergic, alpha; D010566:Virulence Factors, Bordetella; D005576:Colforsin; D015016:Yohimbine; D003571:Cytochalasin B; D000068438:Brimonidine Tartrate; D004815:Epidermal Growth Factor; D010109:Oxymetazoline; D003513:Cycloheximide; D019833:Genistein; D000242:Cyclic AMP; D037342:Pertussis Toxin