[Cryopreservation of in vitro fertilized embryos from transgenic rat by ultrarapid freezing].

We cryopreserved pronuclear stage-embryos from the Transgenic rats produced by introducing the rat GH antisense transgene, by ultrarapid freezing. The embryos were obtained by fertilization in vitro with the sperm of homozygous males for the transgene. After thawing of a part of cryopreserved embryos (97 embryos), the 40 embryos (41%) were morphologically normal, and were transferred to oviducts of recipients. All four live young (10%) obtained (one male and three females) preserved the transgene and exhibited dwarfism. We also produced the homozygous transgenic rats after brother-sister mating of those young. These results demonstrated the possibility of the cryopreservation of embryos by ultrarapid freezing for sustaining transgenic rat line.