A novel oocyte maturation arresting factor in the central nervous system of scallops inhibits serotonin-induced oocyte maturation and spawning of bivalve mollusks.
Serotonin (5-hydroxytriptamine; 5-HT) is a major neurotransmitter that triggers oocyte maturation and sequential spawning in bivalve mollusks. A proteinous and heat-labile substance that proved to be a novel inhibitor of 5-HT-induced egg release from ovarian tissue was found in the cerebral and pedal ganglia (CPG) of the scallop Patinopecten yessoensis. The same inhibitory activity was also observed in the proteinous fraction from the supernatant of hemolymph. Histological observation demonstrated that the novel inhibitor prevented 5-HT from inducing oocyte maturation in the scallop ovary and that no prostaglandin F2alpha (PGF2alpha) inhibited 5-HT-induced oocyte maturation, although PGF2alpha strongly prohibited 5-HT-induced egg release through the gonoduct from ovarian tissue. The novel inhibitor from the scallop CPG also prohibited 5-HT-induced oocyte maturation of other bivalve species as well as scallops. The novel inhibitor, mediated through a receptor mechanism on oocyte membranes, blocked extracellular Ca2+ uptake into oocytes, which was observed in 5-HT-induced oocyte maturation. It is suggested that the novel inhibitor with a molecular mass of 60 kDa, named oocyte maturation arresting factor, which appears to be a universal substance for bivalve species, may be transported from the CPG to the ovary via hemolymph and may prohibit 5-HT-induced oocyte maturation due to the interference of extracellular Ca2+ influx into oocytes, eventually resulting in the inhibition of spawning. On the other hand, it seems that PGF2alpha inhibits 5-HT-induced transport of mature eggs through the gonoduct.
Laboratory of Integrative Aquatic Biology, Field Science Center, Graduate School of Agricultural Science, Tohoku University, 15 Konorihama-Mukai, Onagawa, Oshika 986-2242, Japan.
Toru
T
Tanabe
Makoto
M
Osada
Keiichiro
K
Kyozuka
Kazuo
K
Inaba
Akihiro
A
Kijima
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002490:Central Nervous System / Q000378:metabolism*; D015237:Dinoprost / Q000502:physiology; D005260:Female; D017952:Ganglia, Invertebrate / Q000502:physiology; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D009865:Oocytes / Q000254:growth & development*; D010060:Ovulation / Q000187:drug effects; D049897:Pectinidae / Q000187:drug effects*; D012623:Seawater / Q000737:chemistry; D012701:Serotonin / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000302:isolation & purification* / Q000378:metabolism
D036341:Intercellular Signaling Peptides and Proteins; D012702:Serotonin Antagonists; C018355:intraovarian peptides; D012701:Serotonin; D015237:Dinoprost; D002118:Calcium