Sensitivity of Preimplantation Mouse Embryos to Abrin

Abstract

The effect of the plant toxin abrin on preimplantation mouse embryos in vitro was studied. Two-cell embryos from C57BL/6J or B6CBA/F1/Bom female X B6CBA/F1/Bom male mice were exposed to abrin for 72 hrs in vitro, in medium containing abrin in concentrations ranging from 0.1 to 10,000 pg/ml. Two-cell mouse embryos were also exposed to corresponding concentrations of ricin in vitro. The effect of abrin was evaluated by daily morphological observation of the embryos up to the blastocyst stage and by measuring DNA, RNA and protein synthesis by radioactive precursor incorporation. The effect of ricin was evaluated by morphological observation of the embryos up to the blastocyst stage. The results showed that 2-cell mouse embryos were highly sensitive to abrin, 1 pg/ml being the lowest concentration of the toxin that significantly inhibited the development of 2-cell embryos to the blastocyst stage. With ricin statistically significant inhibition of blastocyst formation was obtained at a concentration of 10 pg/ml. The ID50 for abrin was calculated to be 24 pg/ml and for ricin 47 pg/ml. A dose-dependent lag period was observed before the effect of abrin or ricin on the formation of blastocysts became evident. Incorporation of 3H-thymidine, 3H-uridine and 14C-leucine into DNA, RNA and protein, respectively, was also inhibited by abrin after different time intervals in culture.