The role of nitric oxide in parthenogenetic activation of pig oocytes: A review

Parthenogenetic activation of mammalian oocytes with artificial stimuli is commonly applied in various reproductive biotechniques, e.g. cloning using nuclear transfer. For this reason, many studies focus on oocyte activation in vitro. Recently we have described the activation of pig oocytes using nitric oxide. This activating stimulus is very specific in many aspects. However, it does not provide an adequate stimulus for parthenogenetic development. It was shown that nitric oxide stimulated some signalling pathways which are inactive in conventional treatments for parthenogenetic activation, e.g. the cGMP-dependent signalling cascade. On the other hand, nitric oxide does not stimulate certain signalling pathways involved in oocyte activation after calcium ionophore, e.g. the PKC signalling cascade. The aim of this review is to characterize the complex processes induced in oocytes after treatment with nitric oxide. Perspectives for further research and the application of nitric oxide for parthenogenetic activation of oocytes are outlined.