title: Plasminogen activator-plasmin system potentiates the proliferation of hepatocytes in primary culture.
abstract: OBJECTIVE
  Liver regeneration after partial hepatectomy is thought to be regulated by various molecules including the components of the plasminogen activator (PA)-plasmin system. We have examined the role of fibrinolytic factors, i.e., tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), and their substrate, plasminogen, in the proliferation of hepatocytes in primary culture.
  
  
  METHODS
  Hepatocyte and nonparenchymal liver cells were isolated from Wistar strain rat by a method perfusing the liver with collagenase. DNA synthesis was assessed by measuring the incorporation of [3H]-thymidine into cellular DNA fraction. tPA, uPA and type-1 plasminogen activator inhibitor (PAI-1) gene expressions were measured by Northern blotting. PA activity was measured by fibrin/agarose plate method.
  
  
  RESULTS
  Cellular density-dependent DNA synthesis was observed in the primary cultured hepatocytes; DNA synthesis was lower at high cell density (1.0 x 10(5) cells/cm(2)) than that at low cell density (0.2 x 10(5) cells/cm(2)). DNA synthesis in the hepatocytes cultured at a low cell density was increased by co-culture with nonparenchymal liver cells. Under these growth-stimulated culture conditions, tPA and uPA mRNAs were induced and up-regulated. On the contrary, the PAI-1 mRNA level was decreased under these conditions, and total PA activity was augmented accordingly. The synthetic plasmin inhibitor tranexamic acid, a competitive inhibitor for the plasmin molecule, and PASI-535, a plasmin active center-directed inhibitor, both suppressed hepatocyte proliferation in a dose-dependent fashion. Anti-plasmin antibody also suppressed hepatocyte proliferation.
  
  
  CONCLUSIONS
  The up-regulation of PA activity for ensuring plasmin activity should be an important mechanism in the proliferation of hepatocytes.
authors.affiliation: Department of Nutrition and Physiology, Nihon University Graduate School of Applied Life Sciences, Kameino 1866, Fujisawa, Kanagawa 252-8510, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Akao
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Hasebe
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Okumura
authors.forename: Hiromi
authors.initials: H
authors.lastname: Hagiwara
authors.forename: Taiichiro
authors.initials: T
authors.lastname: Seki
authors.forename: Toyohiko
authors.initials: T
authors.lastname: Ariga
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002455:Cell Division; D004247:DNA / Q000096:biosynthesis; D005341:Fibrinolysin / Q000502:physiology*; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000166:cytology* / Q000187:drug effects; D008115:Liver Regeneration / Q000187:drug effects; D010958:Plasminogen / Q000502:physiology; D010960:Plasminogen Activators / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000502:physiology; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D010958:Plasminogen; D004247:DNA; D010960:Plasminogen Activators; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D014568:Urokinase-Type Plasminogen Activator