Abstract: 43

INDUCTION OF PIG OOCYTE ACTIVATION VIA AN INCREASE IN TYROSINE KINASE ACTIVITY.

Jae-Hwan Kim^{1 *}, Hyun-Jin Do¹ , Wei-Hua Wang^{1 *}, Yong-Mahn Han^{1 *}, Billy Day^{1 *}, Randall Prather^{1 *}
Department of Animal Science, University of Missouri, Columbia, MO ¹

Oocyte activation refers to global changes in the oocyte after the interaction of sperm and oocyte plasma membrane. To date, there are few reports on the mechanism of oocyte activation. This study was conducted to determine whether a protein tyrosine kinase (PTK) activity is involved in pig oocyte activation. After maturation in NCSU 23 medium for 47h, oocytes were treated with 1mM sodium orthovanadate (NaV), an activator of certain protein tyrosine kinases. After treatment for 7h, pronuclear formation, cortical granule (CG) exocytosis, and mitogen-activated protein kinase (MAPK) activity were investigated. To confirm whether oocyte activation is triggered by an increase in PTK activities, immunoblotting with an antibody specific for phosphotyrosine was performed after a 7hr treatment with NaV. Oocytes were also preincubated for 1h with Tyrphostin 47, a specific inhibitor of PTK, and then the oocytes were incubated for an additional 7h in the presence of NaV and Tyrphostin 47. A 7h treatment of oocytes with 1mM NaV caused more than 90% pronuclear formation, CG exocytosis, and a decrease in MAPK activity. Immunoblotting showed that at least three oocyte proteins whose phosphotyrosine contents were significantly increased upon treatment of oocytes with 1mM NaV. Preincubation of pig oocytes with 50µM Tyrphostin 47 completely inhibited the ability of NaV to trigger activation events such as pronuclear formation, CG exocytosis, and a decrease in MAPK activity. These results indicate that pig oocyte activation is induced by an increase in PTK activity stimulated by NaV, and the stimulation of TK signals a series of intracellular changes that lead to the activation events associated with fertilization.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.