Modifications of the Ca2+ release mechanisms of mouse oocytes by fertilization and by sperm factor.
A cytosolic factor from sperm (SF) is thought to be responsible for the generation of intracellular calcium oscillations ([Ca2+]i) associated with fertilization in mammalian oocytes. Whether or not mouse oocytes injected with SF exhibit modifications of their Ca2+ release mechanisms similar to those observed in fertilized oocytes is not known and this was investigated here by injecting porcine SF (pSF). First, pSF-activated oocytes injected with CaCl2 showed persistent sensitization of the Ca2+-induced Ca2+ release mechanism, but this sensitization was absent in SrCl2-activated oocytes. Second, pSF-injected oocytes re-initiated oscillations when fused with untreated oocytes, although the Ca2+ responses were short-lived compared to those initiated by fertilization. Likewise, in the presence of colcemid, pSF-initiated oscillations were prolonged but ceased in advance of those in fertilized zygotes. Also, pronuclear envelope breakdown induced by okadaic acid was not associated with Ca2+ release in pSF-generated zygotes, whereas it was observed in fertilized zygotes. Finally, roscovitine, an inhibitor of maturation promoting factor, blocked pSF-induced [Ca2+]i oscillations. Together, these results show that pSF-induced [Ca2+]i responses exhibit properties similar to those triggered by the sperm, although the SF's Ca2+ active component(s) may be less stable or more susceptible to degradation, resulting in shorter modification of the oocyte's Ca2+ release mechanisms.
Gordo
Ana Carla
AC
Department of Veterinary and Animal Sciences, University of Massachusetts, Amherst, MA 01003, USA.
Kurokawa
Manabu
M
Wu
Hua
H
Fissore
Rafael A
RA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D003703:Demecolcine / Q000378:metabolism; D005260:Female; D005306:Fertilization / Q000502:physiology*; D008297:Male; D008540:Meiosis / Q000502:physiology; D051379:Mice; D009865:Oocytes / Q000378:metabolism*; D011687:Purines / Q000378:metabolism; D000077546:Roscovitine
D011687:Purines; D000077546:Roscovitine; D002122:Calcium Chloride; D002118:Calcium; D003703:Demecolcine