2007 Fiscal Year Final Research Report Summary
Study of action mechanism of gonad-stimulating hormone (GSS) in starfish
| Project/Area Number |
18570056
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Morphology/Structure
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| Research Institution | Tokyo Gakugei University |
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Principal Investigator |
MITA Masatoshi Tokyo Gakugei University, Faculty of Education, Professor (50190674)
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| Project Period (FY) |
2006 – 2007
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| Keywords | Oocyte maturation / Gonad stimulating hormone / Reproductive biology / Starfish |
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| Research Abstract |
Similar to that in vertebrates, resumption of meiosis in starfish oocytes is controlled by hormonal action. Previously, the gonad-stimulating substance (GSS) that acts as gonadotropin was purified from the starfish (Asterina pectinifera) and subsequently, its structure was deciphered. Here, we show that hormonal action of GSS on oocyte maturation of starfish A. pectinifera. Based on biological activity, GSS was principally distributed to radial nerves and nerve rings. A trace amount of genitalin was also contained in cardiac stomach and tube-feet, but it was undetectable in the ovaries and testes. Furthermore, the genitalin activity was detectable in coelomic fluid of animals during spawning, though there was no detectable activity in the fluid from animals before or after spawning.
It has also been demonstrated that GSS acts on the ovary to produce the second mediator 1-methyladenine (1-MeAde) which is the maturation-inducing hormone of starfish. 1-MeAde is produced by ovarian follicle cells around oocytes upon stimulation with GSS. The synthetic genitalin stimulated follicle cells in ripe ovaries to produce 1-MeAde through arise in cyclic AMP (cAMP). However, neither 1-MeAde nor cAMP production occurred in follicle cells during the growing stage in the presence of genitalia. According to competitive experiments using radioiodinated and radioinert genitalin in follicle cells, the Kd value in the ripe stage was lower than that in the growing stage, although similar Bmax values were obtained in both stages. It seems that the affinity of receptors for genitalin in ovarian follicle cells becomes high enough to activate G-proteins and adenylyl cyclase following the breeding season. These findings suggest that, upon spawning, the genitalin secreted from nervous system to the coelomic fluid acts on 1-MeAde production by follicle cells to induce oocyte maturation.
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