Evidence for the synthesis and release of a glycoprotein by mouse blastocysts

Mouse blastocysts were incubated in microdrop cultures in the presence of D-[6-3H]glucosamine. The embryos and the incubation medium were analysed for the incorporation of label into acid-precipitable material. Of the precursor incorporated into blastocysts, 8-13% was detected in the medium. Several glycoproteins were found in the blastocysts and one of molecular weight about 87 000 was also detected in the extracellular medium. In the presence of tunicamycin, the amount of the labelled glycoprotein was reduced by 30-40% in the embryos and 47-69% in the medium. However, the same relative proportion of label was still detected in the extracellular fraction of 87 000 mol. wt. The study demonstrates the synthesis and release of a glycoprotein by mouse blastocysts, the mechanism of which is tunicamycin-insensitive.