1989 Fiscal Year Final Research Report Summary
Studies on the Signal Transduction and Nuclear Binding Site of Epidermal Growth Factor in Rat Livers
| Project/Area Number |
63570535
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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 |
内分泌・代謝学
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| Research Institution | Tottori University |
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Principal Investigator |
ICHII Shogo Tottori Univ. School of Medicine Professor, 医学部, 教授 (80032150)
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| Co-Investigator(Kenkyū-buntansha) |
SATOH Yukio Tottori Univ. School of Medicine Assistant, 医学部, 助手 (70144657)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Epidermal Growth Factor / Epidermal Growth Factor Receptor / Epidermal Growth Factor Receptor mRNA / Nuclear Binding Site / Fetal Liver / Newborn Rat Liver / Regenerating Rat Liver / Autophosphorylation |
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| Research Abstract |
1. Binding sites for epidermal growth factor (EGF) were observed in purified nuclear fraction from rat liver. The binding data yielded a curvilinear Scatchard plot which was decomposed into two binding components with different binding affinities. The binding component with higher affinity (Kd=10^<-10>M) represented approximately 15% of the total binding. The ligand-dependent autophosphorylation, one of the characteristic features of EGF receptor in the plasma membrane, was not observed in the nuclear fraction. The binding capacity in the nuclear fraction increased in contrast to the decrease in the microsomes during the course of liver regeneration after partial hepatectomy.
2. The binding of EGF and activity of EGF-receptor autophosphorylation and of tyrosine-specific protein kinase were determined in hepatic membrane fractions from fetal, newborn and hepatectomized adult rats and compared with those of adult control rats. Although the EGF binding was decreased, there was a tendency for the activity of autophosphorylation to be higher and ligand-dependency to be lower in the membranes from growing hepatic tissues. The activity of tyrosine kinase was higher but less responsive to the ligand in the growing rat hepatic tissues.
3. EGF-receptor mRNA expression in livers of newborn, adult control and partially hepatectomized rats were examined by Northern blot analyses. A human EGF-receptor cDNA was hybridized to RNA species of 10, 6 and 3 Kb. These mRNA were profoundly decreased in livers from newborn rats and relatively decreased in regenerating rat livers.
These results, together with previous observations suggest that contributions of EGF to growth stimulation in these ontogenically different hepatic tissues may be different. Molecular natures and physiological. significance of the nuclear binding sites for EGF still remained to be obscure and will have to be clarified.
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Research Products
(6 results)
