The Effect of Glucose-, Arginine- and Leucine-deprivation on Mouse Blastocyst OutgrowthIn Vitro

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Abstract
To estimate the degree of trophoblast outgrowth in vitro, mouse blastocysts obtained after delay of implantation were cultured either in a modified Brinster medium or in the same medium with exclusion of various combinations of glucose, arginine and leucine. Trophoblast outgrowth was prevented only in a medium from which all three substances were excluded. In this medium the blastocysts remained expanded for 5 days without signs of trophoblast outgrowth - a growth arrest in vitro. After transfer of blastocysts growth arrested in vitro for 5 days to a complete medium including both glucose and the two amino acids, normal outgrowths occurred within two or three days. The growth-arrested blastocysts also developed normally for at least one week when transplanted into salpingectomized foster mothers. It is concluded that blastocyst activation in vitro can be controlled by a few nutrients in a way reminiscent of the activation prior to implantation in utero. Blastocysts activated in utero by systemic administration of oestrogen for various lengths of time before the start of culture, or in vitro by preincubation in a medium containing glucose and all amino acids, also grew out in the growth arrest medium if they had been activated for a sufficiently long time, 18 h in utero and 1 h in vitro, thus indicating that when a blastocyst has reached a certain degree of activation its growth can not be arrested by exclusion of glucose, arginine and leucine.