Abstract
To evaluate the function of protein kinase C (PKC) during oocyte activation following fertilization, the effects of activators and inhibitors of PKC on the second polar body emission, pronuclear formation and protein phosphorylation of mouse oocytes were investigated during in vitro fertilization and during artificial oocyte activation with Ca ionophore (A23187). One ng/ml of 12-O-tetradecanoyl phorbol 13-acetate (TPA), a PKC activator, accelerated PF without accelerating the second polar body emission. 5-20 ng/ml of TPA suppressed the second polar body emission significantly but did not inhibit female chromosome separation of second meiotic division. Staurosporine, a PKC inhibitor, at 1-5 nM, suppressed the second polar body emission. Female chromosome separation was also suppressed by staurosporine and H7, an another PKC inhibitor. One diploid female pronucleus was formed in an egg or an oocyte without the second polar body emission. TPA itself caused female chromosome separation even in the presence of 20 μM of BAPTA-AM, a selective membrane-permeable calcium chelator. These results show that PKC has supportive effect on pronuclear formation. The activation of PKC is indispensable for female chromosome separation during fertilization.
