A protein tyrosine phosphatase inhibitor, sodium orthovanadate, causes parthenogenetic activation of pig oocytes via an increase in protein tyrosine kinase activity.
This study was conducted to determine whether a protein tyrosine kinase (PTK) activity is involved in the initiation of the events that occur at fertilization in pig oocytes. After maturation for 47 h, a 7-h treatment of oocytes with 1 mM sodium orthovanadate, which is an inhibitor of protein tyrosine phosphatase, caused more than 90% pronuclear formation, cortical granule exocytosis, and a decrease in mitogen-activated protein kinase activity. Immunoblotting with an antibody specific for phosphotyrosine showed at least three proteins whose phosphotyrosine contents were significantly increased upon treatment of oocytes with 1 mM sodium orthovanadate. Preincubation of pig oocytes with 50 microM tyrphostin 47, a specific PTK inhibitor, completely blocked the ability of sodium orthovanadate to trigger activation events. In addition, when oocytes were pretreated with the calcium-chelating agent BAPTA-AM, sodium orthovanadate-stimulated pronuclear formation was significantly (P < 0.01) reduced (94.0% vs. 43.1%). These results suggest that PTK may be involved in pig oocyte activation in a calcium-dependent manner and that the stimulation of tyrosine kinase is able to signal a series of intracellular changes that lead to the activation events associated with fertilization.
Kim
J H
JH
Department of Animal Science, University of Missouri, Columbia, Missouri 65211, USA.
Do
H J
HJ
Wang
W H
WH
Macháty
Z
Z
Han
Y M
YM
Day
B N
BN
Prather
R S
RS
D000818:Animals; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D005260:Female; D005307:Fertilization in Vitro / Q000662:veterinary; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009865:Oocytes / Q000201:enzymology*; D010312:Parthenogenesis / Q000187:drug effects*; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors*; D013552:Swine; D020032:Tyrphostins / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology*
D002614:Chelating Agents; D004791:Enzyme Inhibitors; D020032:Tyrphostins; C060152:tyrphostin 47; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D014638:Vanadates; D004533:Egtazic Acid; D020928:Mitogen-Activated Protein Kinases; D017027:Protein Tyrosine Phosphatases