Thapsigargin induces meiotic maturation in surf clam oocytes.
I report here that thapsigargin, an inhibitor of Ca(2+)-ATPase activities in internal Ca2+ stores, induces meiotic maturation in prophase I-arrested surf clam (Spisula solidissima) oocytes. The half-maximal dose for triggering germinal vesicle breakdown (GVBD) is 120 nM. Thapsigargin-induced GVBD is followed by all normal subsequent steps of meiotic maturation including extrusions of first and second polar bodies, with almost normal timing as compared with K(+)-induced activation. Thapsigargin-induced GVBD requires the presence of external Ca2+ at a half-maximal concentration of 0.6 mM. In normal sea water, thapsigargin-induced activation is accompanied by a slightly increased 45Ca2+ uptake by the oocytes and by an intracellular pH rise of 0.3 U. These results show that thapsigargin-sensitive Ca2+ pools regulating Ca2+ fluxes exist in surf clam oocytes, and they also further establish that Ca2+ ions are the major initial trigger for meiosis resumption in this species.
Dubé
F
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Département d'Océanographie, Université du Québec, Rimouski, Canada.
D000818:Animals; D049872:Bivalvia; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008540:Meiosis / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D011188:Potassium / Q000494:pharmacology; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
D013729:Terpenes; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium