The increase in egg metabolism triggered by fertilization initiates the meiotic exit and participates in organizing the maternal and paternal centrosomes of the first mitotic spindle. In the mouse, unfertilized oocytes have all constituents needed to organize a bipolar mitotic apparatus but we don't know whether changes in the reducing power of the NAD(P)H co-factor induced by parthenogenetic agents can generate aberrant centriole distribution in parthenogenetic cell lines. In the present experiment, we activated freshly ovulated mouse eggs by a series of Ca2+ signals either in the presence of lactate which is a high cytosolic reducing agent or, in the presence of pyruvate which is a high cytosolic oxidant.