| Project/Area Number |
62570324
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Gastroenterology
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| Research Institution | Tottori University |
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Principal Investigator |
IKAWA Shiro Division of Chemistry, Institute of Steroid Research, Tottori University School, 化学部門, 教授 (70032183)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAKE Mariko , 医学部附属ステロイド医学研究施設・化学部門, 助手 (20135883)
MURA Tetsuo , 医学部附属ステロイド医学研究施設・化学部門, 講師 (80093631)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1988: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1987: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Primary cultured hepatocytes / Sterol and bile acid / Cell density / 毛細胆管の再生機構 / cell surface modulator / 加齢肝細胞機能と組織化 / cell surtace modcelator / 肝細胞の組織化と機能 / 加齢によるcell surface modulatorの糖鎖 / 細胞密度依存性と機能 / gap junction / 不定期DNA合成 |
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| Research Abstract |
Cell-cell contact is known as an important fator in cell growth and tissue formation. The density of hepatocytes in the liver estimated as about 3 x10^5 cells/cm^2, which is twice that in primary culture. In these conditions, in general, hapatocytes do not grow as they are in the G_o state of the cell cycle and show freely differentiated phenotypes. This paper reports growth and development of differentiated functions in primary culture of normal and pre-malignant hepatocytes of regenerating rat liver with special reference to cell density and cell functions. (1) In hepatocytes cultured at low cell density ( 2 x10^4 cells/cm^2 ), the ratio (T/G) of taurine conjugated bile acids (T) to glycine conjugated bile acids(G) was decreased. Conversely, in hepatocytes cultured at high cell density (1x10^5 cells/cm^2), the ratio was increased. (2) Cholesterol synthesis in cultured hepatocytes was greater at low cell density, whereas triglyceride synthesis was much higher at high cell density. (3)
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Isolated plasma membrane was prepared from rat liver. The ratio of bile acid conjugation with amino acids was markedly enhanced in hepatocytes at low cell density by addition of this plasma membrane. The effect of the plasma membrane was dose-dependent and reached a maximum at the concentration of 300 g of membrane protein per 35 mm dish. (4) Addition of plasma membranes also affected the basal activities of 5'-nucleotidase, alkaline phosphatase and Na^+ , K^+ -ATPase of cells at low cell density. (5) The ability of hepatic plasma membrane to mimic the reciprocal effect of increased cell density on cellular activities was almost lost in Ca^<2+> abd Mg^<2+>-free medium.
These results in vitro suggest that various functions of hepatocytes in vivo at the mature state and during development and regeneration are all regulated by cell-cell contact and that many functions are not maintained unless the cells from tissue receive complex regulation from cytosocial environment. Therefore, cell surface modulators involved in the regulations of cell functions by cell density do not possibly induce new expression of dormant genes, but regulate phenotypic genes that have already been switched on during terminal differentiation.
It would be interesting to know whether the cell surface modulator is responsible for inhibition of related to growth functions and stimulation of hepatocyte characters. This problem must be examined by further purification and characterization of the cell surface modulator responsible for these activities. Less
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