| Project/Area Number |
07454226
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生物形態・構造
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| Research Institution | Waseda University |
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Principal Investigator |
KIKUYAMA Sakae Dept Biol, School Educ, Waseda Univ.Professor, 教育学部, 教授 (20063638)
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| Co-Investigator(Kenkyū-buntansha) |
KIKUTA Toshiteru Dept Biol, School Educ, Waseda Univ., 教育学部, 助手 (80267468)
TAKAHASHI Noriyuki Res Inst.Human Sci, Res. Assoc., 人間綜合研究センター, 助手 (80267450)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥7,800,000 (Direct Cost: ¥7,800,000)
Fiscal Year 1996: ¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1995: ¥4,800,000 (Direct Cost: ¥4,800,000)
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| Keywords | pituitary / amphibians / prolactin / growth hormone / gonadotropin / paracrine / autocrine / regulation of secretion / ホルモンの共存 / 両生類下垂体 / ホルモン分泌調節 / 糖タンパクホルモンのαサブユニット |
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| Research Abstract |
Hormonal messenger molecules are released from specific cells into the general circulation to reach distant target cells. However, the molecules can also be released to influence the function of neighboring cells as paracrine or autocrine system.
In the bullfrog pituitary, PRL cells frequently located in contact with gonadotropin cells. It was found that PRL enhances the responsiveness of LH cells to GnRH in vitro. The responsiveness to GnRH became less conspicuous as the cell density was reduced. Addition of PRL to the medium enhanced the responsiveness to the secretagogue, and addition of antiserum against PRL lowered the responsiveness to a certain extent. Secondly, experiments were performed to study the effect of free alpha-subunit of glycoprotein hormones existing in the secretory granules of PRL.It was found that addition of alpha-subunit into the culture medium enhanced the release of PRL.On the other hand, we have found that a considerable number of cells exhibited secretion of
… More
both PRL and GH when the pituitaries were dispersed and cultured. This suggested that either transcription or translation of PRL and/or GH had been blocked until the cells were dispersed and cultured. Cycloheximide blocked the appearance of such cells. These findings indicated that the cells secreting both PRL and GH after dispersal and culture possessed the mRNAs for these hormones before they were transferred to an in vitro system. In addition, several of the PRL-immunoreactive cells possesses GHmRNA.Prolactin mRNA was also expressed in several of the GH immunoreactive cells.
In conclusion, paracrine and autocrine regulation of pituitary cell function in amphibians were elucidated : (1) PRL acts directly on gonadotrophs to enhance their responsiveness to GnRH in a paracrine fashion. (2) Both translation of PRL mRNA in GH cells and translation of GH mRNA in PRL cells are triggered by cell dispersion and/or culture, suggesting the presence of paracrine factors that inhibit the translation of PRLmRNA in GH cells and of GHmRNA in PRL cells. (3) Alpha-subunit secreted by PRL cells acts as an autocrine and/or paracrine factor to enhance the release of PRL. Less
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