Effect of Delayed Implantation on Dry Weight and Lipid Content of Mouse Blastocysts

Abstract

Blastocysts from ovariectomized mice treated with progesterone in oil or oil only were freeze-dried and weighed with a Lowry quartz fiber balance to determine whether or not significant changes in weight occur during the prolonged free living phase of delayed implantation. An increase in weight of blastocysts from progesterone and oil-treated animals was observed until day 10 of delayed implantation. Between day 10 and day 30, the weight of blastocysts from progesterone-treated animals changed little, while the weight of blastocysts from oil-treated animals increased steadily. These results demonstrate that delayed implanting mouse blastocysts accumulate more exogenous material than they consume and, thus, that depletion of stored nutrients does not appear to be a limiting factor in their survival. Furthermore, it is shown that progesterone influences the balance between uptake and utilization of exogenous materials by the embryos during delayed implantation.