CRYOPRESERVATION OF IN-VITRO FERTILIZED E MBRYOS FROM TRANSGENIC RAT BY ULTRARAPID FREEZING

We cryopreserved pronuclear stage-embryos from the Transgenic rats pro duced by introducing the rat GH antisense transgene, by ultrarapid fre ezing. The embryos were obtained by fertilization in vitro with the sp erm of homozygous males for the transgene. After thawing of a part of cryopreserved embryos (97 embryos), the 40 embryos (41%) were morpholo gically normal, and were transferred to oviducts of recipients. All fo ur live young (10%) obtained (one male and three females) preserved th e transgene and exhibited dwarfism. We also produced the homozygous tr ansgenic rats after brother-sister mating of those young. These result s demonstrated the possibility of the cryopreservation of embryos by u ltrarapid freezing for sustaining transgenic rat line.