Porcine oocyte activation induced by a cytosolic sperm factor.
It is not known how the fertilizing sperm elicits the release of Ca(2+) from the oocyte's intracellular stores. We investigated whether a crude extract isolated from boar sperm could induce the Ca(2+) release and trigger subsequent early and late activation events upon injection into matured porcine oocytes. The sperm extract induced an immediate rise in the intracellular free Ca(2+) concentration in all oocytes tested, which was followed by repetitive Ca(2+) transients in 11 out of 14 oocytes. Heat or trypsin treatment of the extract totally abolished the Ca(2+) releasing activity of the sperm factor. The injected oocytes showed cortical granule exocytosis, they resumed meiosis and entered first interphase: pronuclei were formed in 89.2% (132/148) of the cases. Pronuclear formation was accompanied by the appearance of a new 22 kDa protein as normally seen at fertilization. Of the successfully injected oocytes 51.7% (105/203) cleaved and 2.0% (4/203) developed to the blastocyst stage after being cultured for 7 days in NCSU 23 medium. Injection of the carrier medium could not trigger these changes. The results indicate that the sperm might activate porcine oocytes by introducing a soluble factor into the oocyte's cytoplasm after gamete fusion.
Macháty
Z
Z
Department of Animal Sciences, University of Missouri-Columbia, Columbia, Missouri 65211, USA. machatyz@missouri.edu
Bonk
A J
AJ
Kühholzer
B
B
Prather
R S
RS
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002457:Cell Extracts; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D008297:Male; D008845:Microinjections / Q000379:methods; D009865:Oocytes / Q000378:metabolism / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism*; D013552:Swine
D002457:Cell Extracts; D002118:Calcium