This study examined the event of
protein phosphorylation in bovine oocytes in response to sperm penetration and parthenogenetic
activation. In vitro matured oocytes were labelled with [32P]orthophosphate at 3 h intervals
from 3 h to 18 h or from 0 h to 12 h following in vitro fertilisation and parthenogenetic
activation, respectively. The level of protein dephosphorylation, at approximately 43 kDa, was similar
in fertilised and parthenogenetically activated bovine oocytes. However, the level of protein
phosphorylation at 40 kDa, 23 kDa and 18 kDa was different between these two samples. There were no
such changes of protein phosphorylation and dephosphorylation in the control oocytes. Further, by
two-dimensional gel electrophoresis there is a difference in the level of protein phosphorylation at
18 kDa between the fertilised and activated oocytes. These results suggest that this protein
phosphorylation may be related to the formation of the male pronucleus in bovine oocytes.