Uptake and incorporation were determined for glutamine and asparagine as well as for nine amino acids which have been shown by culture experiments in vitro to be important in the development of the preimplantation mouse embryo. In general, there was a tenfold increase in the incorporation and a fivefold increase in uptake of the amino acids from the one-cell to the morula stage. The largest change in both incorporation and uptake occurred at about the eight-cell stage of development.
Leucine was incorporated more, and glutamine taken up in larger quantities, than the other amino acids. The rate of incorporation of leucine carbon into the embryo between the one- and two-cell stage was 0·208 and for the morula to blastocyst was 2·153 pmol/embryo/hr. The total uptake of glutamine carbon between the one- and two-cell stage was 1·768 and between the morula and blastocyst was 5·655 pmol/embryo/hr.
Fertilization of the mouse ovum did not significantly affect incorporation of leucine and had only a small effect on total uptake of leucine. This contrasts with the findings in invertebrates where fertilization results in a marked increase in all aspects of amino acid metabolism.
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