Calcium, calcium release receptors, and meiotic resumption in bovine oocytes.
During maturation, mammalian oocytes undergo a series of changes that prepare them for fertilization. These events are regulated by kinases, most notably histone H1 and mitogen-activated protein kinase. Intracellular calcium ([Ca2+]i) oscillations participate in oocyte signaling, and it has been postulated that they play a role in oocyte maturation. In these studies we investigated the association of Ca2+, Ca2+ channels, and activation of kinases in in vitro-maturating bovine oocytes. BAPTA-AM, a Ca2+ chelator, inhibited oocyte maturation and delayed activation of kinases, although spontaneous [Ca2+]i rises were not observed in control oocytes loaded with fura-2, a Ca2+ indicator. The ability of the 1,4,5-inositol trisphosphate receptor (InsP3R) to release Ca2+, monitored after the addition of thimerosal and myo-inositol 1,4,5-trisphosphate (InsP3), increased as maturation progressed. This may be associated with a similar increase, monitored by Western blotting, in the density of the type I InsP3R isoform during oocyte maturation. Injection of heparin, an InsP3R antagonist, blocked oocyte maturation and activation of kinases. The density of the ryanodine receptor, another Ca2+ channel, may be 30- to 100-fold lower than that of the InsP3R in bovine oocytes. Thus, our results demonstrate that [Ca2+]i participates in the progression of meiosis and that the InsP3R may be responsible for the majority of Ca2+ release during maturation and fertilization.
He
C L
CL
Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst 01003, USA.
Damiani
P
P
Parys
J B
JB
Fissore
R A
RA
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D002417:Cattle; D002614:Chelating Agents / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors; D007700:Kinetics; D008540:Meiosis / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D009865:Oocytes / Q000201:enzymology / Q000254:growth & development / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000819:agonists / Q000037:antagonists & inhibitors
D015220:Calcium Channels; D002614:Chelating Agents; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D011494:Protein Kinases; D002118:Calcium