Effects of low sodium concentrations on the development of post-implantation rat embryos in culture and on their sensitivity to anticonvulsants

Embryotoxicity of carbamazepine in rat postimplantation embryo culture after in vitro exposure via three different routes

Postimplantation rat embryo culture is used widely for studies of embryotoxic effects on the isolated embryo after in vitro exposure to xenobiotic compounds. In this study, the relevance of three routes of exposure of the embryo in vitro was evaluated using the embryotoxic anticonvulsant carbamazepine. Embryotoxic effects were assessed, and analyses in conceptus tissues were done to reveal uptake and metabolism of the compound. Exposure via the culture medium resulted in neural tube defects and general retardation of growth and development. After injections into the amniotic or exocoelomic space, local membrane adhesions were found. Intra-amniotic exposure caused adhesions of the amniotic membrane with the embryonic neural plate, resulting in trapping of the membrane in the closing neural tube, as well as in open neural tube defects occurring in various areas of the neural tube. Only after exposure via the culture medium were amounts of carbamazepine detectable in the embryonic tissue, correlating with the systemic effects found. It is concluded that uptake from the culture medium via the yolk sac circulation is the relevant exposure route to be used for embryotoxicity effect assessment.

Interlaboratory evaluation of embryotoxicity in the postimplantation rat embryo culture

The embryotoxicity of eight xenobiotic compounds in rat postimplantation whole embryo culture was blindly tested in four laboratories according to a standard protocol. The results show that the four nonteratogens amaranth, penicillin, isoniazid, and saccharin did not affect embryogenesis apart from general toxicity at very high concentrations in culture for amaranth and isoniazid. There was good concordance of results across the laboratories. The four teratogens (retinoic acid, 6-aminonicotinamide, acetylsalicylic acid, and vincristine) induced a variety of specific embryotoxic effects, which were in most cases similar in all laboratories. These results indicate that the definition for specific embryotoxicity used, as well as the culture duration and embryonic age are crucial for concordant scoring. Other methodologic differences did not significantly influence scoring of embryotoxicity. Therefore, within the limits of the end points and embryonic stage represented in the method, embryo culture appears as a useful method for embryotoxicity screening, which can be reproducibly applied in different laboratories.