Short-Term Exposure of Two-Cell Hamster Embryos to Collection Media is Detrimental to Viability

Hamster 2-cell embryos were transferred to recipients to provide information on the block to development in vitro. Previous attempts to elucidate this block have focused on possible deficiencies in the culture medium. In this study the possibility was examined that the media used for embryo collection are actually embryotoxic. Two-cell embryos obtained from superovulated mated ham-sters were exposed to collection media [either a Hepes-buffered modified Tyrode’s solution (TALP-Hepes) or PB1 I during either a “fast transfer ” procedure (time elapsed from collection to transfer 3.9 ± 0.7 mm or 3.7 ± 0.9 mm, respectively) or a “slow transfer ” procedure (time elapsed 19.1 ± 4.4 mm or 20.8 ± 5.7 mm, respectively). In each transfer experiment, equal numbers of embryos from the same donor pooi were transferred to one oviduct (fast transfer) and to the contralateral oviduct (slow transfer) of the same recipient. Embryos were recovered 33-36 h after transfer; embryos developing at least to the 8-cell stage were considered viable. Significant differences were found (P<O.005) between the viability of embryos subjected to fast and slow transfer procedures using either TALP-Hepes (embryo survival 60.8 % vs. 22.2%, respectively, difference 38.6%) or PB1 (survival 50.6 % vs. 10.5%, respectively, difference 40.1%). These data show that length of ex-posure to collection media is an important variable in determining subsequent developmental ability of 2-cell hamster embryos. These media are suitable for embryos of other species but apparently provide an environment that is detrimental to hamster 2-cell embryos, which must be unusually sensitive. This detrimental effect needs to be eliminated before any deficiency of the culture environment for hamster embryos can be identified and corrected