title: Spontaneous and fertilization-induced Ca2+ oscillations in mouse immature germinal vesicle-stage oocytes.
abstract: Mouse germinal vesicle (GV)-stage oocytes not only show Ca2+ oscillations in response to fertilization but also exhibit spontaneous Ca2+ oscillations during meiotic maturation in vitro. Spontaneous Ca2+ oscillations were entirely suppressed by microinjection of heparin (25 microM final intracellular concentration), an antagonist of inositol trisphosphate (IP3) receptor, whereas fertilization-induced Ca2+ oscillations were only partially inhibited by heparin even at a high dosage of 600 microM. Inhibition of endogenous IP3 generation by antagonizing phospholipase C using U73122 (20 microM final concentration) also failed to suppress the generation of fertilization-induced Ca2+ transients, suggesting that the two types of Ca2+ oscillations do not have the same dependence on IP3-induced Ca2+ release. In addition, spontaneous Ca2+ oscillations require the presence of intact GV whereas fertilization-induced Ca2+ oscillations are independent of the GV but require cytoplasm, since enucleation eliminated only spontaneous Ca2+ oscillations but not fertilization-induced Ca2+ oscillations. These results suggest that IP3-induced Ca2+ release is the primary mechanism responsible for spontaneous Ca2+ oscillations. Sperm-induced Ca2+ oscillations, however, may employ more complex mechanisms during fertilization.
authors.affiliation: Institute of Developmental Biology, Chinese Academy of Sciences, Beijing, People's Republic of China.
authors.forename: M Q
authors.initials: MQ
authors.lastname: Deng
authors.forename: X Y
authors.initials: XY
authors.lastname: Huang
authors.forename: T S
authors.initials: TS
authors.lastname: Tang
authors.forename: F Z
authors.initials: FZ
authors.lastname: Sun
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000032:analysis; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005306:Fertilization / Q000502:physiology*; D005307:Fertilization in Vitro; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D008540:Meiosis; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis
chemical_list: D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D003994:Bucladesine; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium