Reproductive Technology

Development of Parthenogenetic Rat Embryos

Abstract

In an effort to establish cloning technology for the rat we have tested several methods (electric stimulation or treatment with ethanol or strontium) for the parthenogenetic activation of rat oocytes. First we observed a marked individual difference between rats of the outbred Wistar strain used for the experiments in their ability to yield activatable oocytes. This was independent of the activation protocol and may be due to a genetic predisposition that is crucial for the parthenogenetic activation of oocytes. Secondly, we observed that the activation of oocytes was dependent upon the time between superovulation of the donor animal and the collection of the embryos. "Aged" oocytes, derived about 24 hrs after superovulation, were more prone to activation by each method than "younger" oocytes and some even underwent spontaneous activation without treatment and exhibited pronuclei formation and blastocyst development. Thirdly, we observed that all activation methods were effective in generating parthenogenetic rat embryos and that rat parthenogenotes can develop until implantation. However, in general, short term (15 min) as well as long-term (2 hrs) strontium treatment proved to be superior to stimulation by ethanol or electric pulse. These results will be helpful in achieving successful cloning in the rat.