Preliminary evaluation of in vitro prescreen assays for developmental toxicants based on cultured murine preimplantation embryos and a cell line developed from a bovine preimplantation embryo.

The purpose of this research was to evaluate in vitro assays and compare their efficiency in accurate prediction of the potential of chemicals to cause abnormal embryonic/foetal development. In vitro assays were based on cultured murine preimplantation embryos and a continuous cell line derived from a bovine preimplantation embryo. Preimplantation embryos collected from superovulated mice were cultured for 72 hr in the presence of 10-fold dilutions of coded compounds. In vitro embryonic development was considered normal if the embryos hatched from the zona pellucida (with normal-appearing inner cell mass and trophoblast cells) and attached to the culture plate at the end of the culture period. The embryonic cells were seeded in 96-well plates, cultured for 24 hr in control media, exposed to 10- and twofold dilutions of test compounds for 72 hr, and finally were stained and counted. The inhibitory concentration (IC(50)) and lethal concentration (LC(50)) were the concentrations (mm) that decreased embryonic development or cell viability by 50%, and were calculated for three model compounds and 10-12 coded compounds (known developmental toxicants and non-toxicants). The concordance between in vivo animal developmental toxicity data and the murine and bovine assays was 83 and 87%, respectively. These accuracies are similar to those of other available assays, and the bovine assay has the added advantage of being simple to perform and economical (about US$100 per assay).