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FEITOSA, W. B. Protein kinase C (PKC) and Calcium/calmodulin-dependent protein kinase II (CaMKII) in bovine oocyte activation. [Proteína quinase C (PKC) e proteína quinase dependente de cálcio/calmodulina (CaMK II) na ativação de oócitos bovinos]. 2010. 87 f. Tese (Doutorado em Ciências) Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, São Paulo, 2010. The intracellular calcium increase resulting from fertilization is necessary for oocyte transition to zygote. The events that occur during this transition are characterized as “activation”, which are dependent on calcium. However the biochemical events that occur during this activation are still not fully elucidated. The protein kinase C (PKC) and the calcium/calmodulin-dependent protein kinase II (CaMKII), are involved in regulating the events of activation, since these proteins have activity during fertilization and are activated by calcium. However there are many doubts about the real role of these proteins in the oocyte activation. Thus, the objective of this study was to evaluate the role of PKC and CaMKII in bovine oocyte activation. For this purpose, in vitro matured bovines oocytes were parthenogenetically activated (PA) by using calcium ionophore A23187 (5μM) for five minutes, and the resumption of meiosis, the cytoskeleton organization and the endoplasmic reticulum (ER) organization were evaluated 1 hour post-activation. In experiment 1, were evaluated the role of CaMKII in these events. The oocytes were PA in the presence or absence of 100μM of CaMKII inhibitor (Autocamtide-2 Related Inhibitory Peptide, Myristoylated). The inhibition of CaMKII did not affect the meiosis resumption and the ER after the PA. However, there was no spindle rotation at telophase II stage when the CaMKII was inhibited. These results showed that although the CamKII has no effect on resumption of meiosis, it participates in the regulation of cell cycle progression after PA of bovine oocytes. In experiment 2, was evaluated the role of PKC on PA bovine oocytes. The oocytes were parthenogenetically activated in the presence or absence of 10μM of PKC inhibitor (Bisindolymaleimide I). The PKC inhibition did not affected the resumption of meiosis and the progression through the cell cycle until the stage of telophase II. However, the ER organization was affected by PKC inhibition. A similar result was obtained when the oocytes were activated in the presence of cytochalasin C, which promotes the depolymerization of the actin filaments. The current experiment showed the participation of the PKC-actin pathway at the ER organization in the bovine oocytes activation.