The uptake of [3H]estradiol by mouse preimplantation embryos in vitro

Mouse blastocysts collected on day 4 were cultured for 20 hours in media containing various concentrations of [3H]estradiol with/without 10(-6) M unlabelled estradiol. There was a significant reduction in the radioactivity of embryos cultured at 4 degrees C compared with that of embryos cultured at 37 degrees C. The radioactivity of embryos kept in the washing solution after washing was slight lower but showed no significant difference when it was compared with that of embryos not kept in this way. There was no significant difference between the radioactivity of embryos cultured in 2 X 10(-8) M [3H]estradiol and that of embryos cultured in 2 X 10(-8)M [3H]estradiol plus 10(-6)M non-labelled estradiol. Furthermore the radioactivity of embryos incubated in 2.5 X 10(-8)M [3H]estradiol is more than twice that of embryos incubated in 10(-8)M [3H]estradiol. These results demonstrate that preimplantation mouse embryos are capable of uptake and retaining of estrogen and that the mechanism of uptake is neither selective nor receptor mediated.