Activation of pig oocytes by intracytoplasmic injection of strontium and barium.
Ovulated mouse oocytes are activated by exposure to culture medium containing Sr2+ or Ba2+ or by intracytoplasmic injection of the divalent cations. It is known that in vitro matured pig oocytes are activated by the intracytoplasmic injection of Ca2+. In this study, we examined the effect of exposure and of intracytoplasmic injection of Sr2+ or Ba2+ on in vitro matured pig oocytes (MII-oocytes). When MII-oocytes were exposed to the medium containing divalent cations, no oocytes were activated. However, in the case of oocytes that were injected with Sr2+, Ba2+ and Ca2+, at 6 h after injection, 64%, 71% and 86% of the oocytes had been released from MII-arrest, and 51%, 67% and 84% formed female pronuclei, respectively. The initial transient in intracellular Ca2+ concentration ([Ca2+]i) was measured by the Ca2+ indicator dye fluo-4 dextran. Microinjection of Sr2+, Ba2+ or Ca2+ induced a rapid elevation of [Ca2+]i. The exocytosis of cortical granules was examined by staining with fluorescein isothiocyanate (FITC)-labelled peanut agglutinin. After an injection of divalent cations, a release of cortical granules was observed in the oocytes. Maturation promoting factor (MPF) activity declined to a low level after 6 h in all the oocytes injected with divalent cations. To test their developmental ability, injected oocytes were treated with cytochalasin B and then cultured for 168 h in NCSU23 medium. After 168 h, 29% (Sr2+), 29% (Ba2+) and 51% (Ca2+) of the oocytes had developed to the blastocyst stage. These results indicate that intracytoplasmic injection of Sr2+ and Ba2+, like that of Ca2+, induces in vitro matured pig oocytes to be released from MII-arrest and leads them into a series of events related to oocyte activation.
Okada
Konosuke
K
Department of Life Science, Graduate School of Science and Technology, Kobe University, Kobe 657-8501, Japan.
Miyano
Takashi
T
Miyake
Masashi
M
D000818:Animals; D001464:Barium / Q000008:administration & dosage / Q000494:pharmacology*; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D005260:Female; D000090204:Mesothelin; D009865:Oocytes / Q000187:drug effects*; D013324:Strontium / Q000008:administration & dosage / Q000494:pharmacology*; D013552:Swine / Q000502:physiology
C000715528:Msln protein, mouse; D001464:Barium; D000090204:Mesothelin; D002118:Calcium; D013324:Strontium