Parthenogenetic Activation of Porcine Oocytes with Guanosine-5′-O-(3′-Thiotriphosphate)1

Abstract

A possible mechanism by which sperm activate oocytes may involve a G protein-mediated signal-transducing pathway. Artificial stimulation of G proteins leads to events very similar to those at fertilization in oocytes of several species. Here we report the effects of activation of a G protein with guanosine-5'-O-(3'-thiotriphosphate) (GTP-gamma-S), a hydrolysis-resistant analog of guanosine triphosphate (GTP), in porcine oocytes. Mature oocytes were injected with 1 mM GTP-gamma-S. In response to injection, oocytes underwent changes normally occurring at fertilization, i.e. cortical granule exocytosis, changes in the protein synthetic profile, pronuclear formation, and development to the blastocyst stage. Guanosine-5'-O-(2-thiodiphosphate) (GDP-beta-S; a metabolically stable analog of guanosine diphosphate [GDP] that inactivates the G protein) and the carrier medium (CM; medium in which the injected compounds were dissolved) were significantly less effective in oocyte activation. It is suggested that porcine oocytes contain the components of a G protein-mediated signaling pathway that might function in oocyte activation at fertilization.