Parthenogenetic activation of mouse oocytes using calcium ionophores and protein kinase C stimulators

Fertilization involves the production of inositol trisphosphate and diacylglycerol with a subsequent increase in intracellular calcium concentration ([Ca2+]i) and the activation of a calcium-dependent protein kinase, the so-called protein kinase C (PKC). Methods of parthenogenetic activation have focused on this calcium wave which seems to be large enough to generate all the responses associated with fertilization and even finally inducing the activation of PKC activity. The specific stimulation of PKC by phorbol esters in turn elicits [Ca2+]i oscillations although no reports exist claiming that the mere activation of this protein is capable of sustaining embryonic development. In this paper we describe the effect of different calcium ionophores and phorbol esters as parthenogenetic agents on mouse oocytes compared with ethanol as the standard procedure. Phorbol esters (OAG) fail to activate a significant number of oocytes, with very few reaching blastocyst stage. However, when a calcium ionophore (A23187) is added, the percentage of embryos reaching the blastocyst stage increases to such an extent that it is the best chemical method assayed to date. We conclude that incubation with both compounds combined inhibits feed-back processes between the above reactions and so induces a more physiologic parthenogenetic activation.