An attempt for obtaining xenogeneic blastocysts (Rat↔Mouse) was undertaken by aggregation method. As a culture medium, Dulbecco's modified eagle medium with 0.3% bovine serum albumin (pH 7.4) was used for the production of xenogeneic chimeric embryos in this experiment.
When the late eight-cell stage rat and mouse embryos were cultured immediately after flushing from the uterus, 88.2%(30/34) of rat embryos and 95.0%(19/20) of mouse embryos developed into expanded blastocyst after 48 hours in culture. When rat and mouse embryos were removed their zona pellucidae with 0.3% pronase before culture, 87.0%(20/23) of rat embryos and 95.7%(22/23) of mouse embryos developed into expanded blastocyst after 48 hours in culture. On the other hand, 87.0%(40/44) of allogenic chimeric rat embryos (Rat↔Rat) and 90.5%(38/42) of allogenic chimeric mouse embryos (Mouse↔Mouse) developed into single, integrated expanded blastocyst after 48 hours in culture respectively. Furthermore, xenogeneic chimeras betwen rat and mouse were produced by aggregating embryos at the late eight-cell stage in this experiment. Out of 41 aggregated embryos from rat and mouse, 34 (82.9%) formed single, integrated expanded blastocyst after 48 hours in culture.
These results showed that Dulbecco's modified eagle medium was available for the production of xenogeneic chimeras between rat and mouse.