In vitro uptake and incorporation of amino acids by blastocysts from intact and ovariectomized mice

Blastocysts were recovered from the uteri of intact or ovariectomized mice and incubated with a mixture of 14C amino acids in vitro. The level of uptake and incorporation of the amino acids as estimated by scintillation counting was higher in blastocysts from intact than in those from ovariectomized animals. Furthermore, when the two types of eggs were “pre‐incubated” for varying periods in non‐radioactive medium and then placed in 14C amino acids, the level of incorporation by blastocysts from intact animals remained constant while that in blastocysts from ovariectomized animals increased with time. The increasing ability to take up and incorporate amino acids in vitro by blastocysts recovered from the uteri of ovariectomized animals suggest that in the absence of ovarian hormones, the uterus exerts a negative influence on the metabolism of the blastocysts. In addition, incubation of the blastocysts with estradiol 17β and/or progesterone did not affect the uptake or incorporation of amino acids suggesting that the hormones do not influence protein synthesis in the eggs by direct action.