Effect of Steroid Sex Hormones on the Development of Early Mouse Embryos In Vitro

Abstract

In vitro culture methods of early mammalian embryos allow an evaluation of pharmacological effects after early maternal treatment on embryonic development (Nature 270, 54, 1977). After maternal administration of the gestagens cyproterone acetate (CA) or medroxygesterone acetate (5–50 mg/kg s.c.) on day 2 of pregnancy (p.c.) we obtained mouse morulae and blastocysts on day 3 p.c. and cultured them in vitro for 120 h. The number of embryos per mother and the blastocyst/morula quotient was not affected. During the in vitro culture the rate of embryos that hatched, attached to the surface of the petri dish, and developed a differentiated trophoblast layer remained constant. However, differentiation of the inner cell mass (ICM) into 2 germ layers was inhibited irrespective of the dose (76% in controls; 44% after treatment). The additional application of estrogen on day 2 p.c. (0.03 μg estron/mouse) did not alter the rate of embryos developing 2 ICM germ layers but reduced the number of blastocysts on day 3. However, the application of a single dose of 0.03 μg estrogen/mother only inhibited the embryonic development in culture.