In vitro methods for the study of the effects of teratogens on preimplantation embryos.

In vitro culture methods are described for mouse embryos during the preimplantation period (Whitten's medium) and for mouse and rat blastocysts during the time of implantation (NCTC-109 medium). Examples are given for the influence of the genetic background (strain differences) on in vitro development and for the detection of a DNA repair mechanism in cultured preimplantation embryos. S-shaped dose effect curves were obtained for the influence of UV-irradiation and cyclophosphamide (CPA) and its metabolites on development of pre implantation mouse embryos treated during in vitro culture. Similar curves were obtained for mouse blastocysts cultured at implantation after treatment of the mother with either CPA or the steroid sex hormones cyproterone acetate (CA) or medroxyprogesterone acetate (MPA). The embryo transplantation technique is described as a teratological method to test the viability of preimplantation mouse embryos which have incorporated the stable isotope 13C during in vitro culture. The importance of the in vitro culture techniques and of the transplantation method in experimental teratology during the earliest period of pregnancy is discussed.