| Project/Area Number |
03454096
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
畜産学(含草地学)
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| Research Institution | THE UNIVERSITY OF TOKYO |
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Principal Investigator |
SAKAI Senkiti Univ. of TOKYO, Fac. of Agriculture, Associate Professor, 農学部, 助教授 (80114487)
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| Co-Investigator(Kenkyū-buntansha) |
AOKI Fugaku Univ. of Tokyo, Fac. of Agriculture, Assistant Professor, 農学部, 助手 (20175160)
KOHMOTO Kaoru Univ. of Tokyo, Fac. of Agriculture, Professor, 農学部, 教授 (30011894)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1992: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1991: ¥3,600,000 (Direct Cost: ¥3,600,000)
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| Keywords | prolactin / prolactin receptor / plasma membrane receptor / mammary gland / hormone-induced dissociation / negative cooperativity / Scatchard plot / Hill plot / レセプタ- / 解離機構 / 高濃度プロラクチン |
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| Research Abstract |
We have cleared two points in the mammary prolactin (PRL) receptor.
(1) PRL accelerated the dissociation of PRL from its receptor in a dose- dependent manner. Scatchard analysis revealed that this reaction is not a simple bimolecular reaction. The Hill plot was non-linear. At PRL higher than 30 ng/ml, the Hill coeficient changed from 1.0 to 0.7. Using the PRL-preloaded receptor, the receptor remained active for association after PRL-induced dissociation. As PRL accelerated the PRL-binding reaction, it was speculated that PRL at high levels can actively generate a hormonal signal. Negative cooperativity is of much biological importance under conditions where levels of hormone are elevated exceedingly or abnormally.
(2) PRL bound to the cell receptor was dissociated by the treatment with acid in a molarity-dependent manner rather than pH-dependent. The ratio of acid-sensitive to acid-insensitive receptor changed independently after parturiton. By acid treatment of subcellular membranes, about 80% of PRL bound with plasma and intracellular membrane receptors were acid-sensitive and acid-insensitive, respectively. We concluded that plasma membrane PRL receptor is intrinsically acid-sensitive and regulated independently.
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