Actin and tubulin synthesis in murine blastocyst outgrowths

The actin and tubulin contents of blastocysts grown in vitro for 72 h were estimated by densitometric analysis of Coomasie-blue stained SDS-gels. Actin represents 7% and tubulin 13% of total blastocyst outgrowth protein. The relative synthesis of these two proteins was measured by two-dimensional electrophoresis utilizing unlabeled and isotopically labeled actin and tubulin internal markers. Actin synthesis constituted 6.3% and tubulin synthesis 1.5% of the total protein synthesis. These values are not significantly different from those we have reported previously for mouse preimplantation blastocysts recovered from uteri. It appears then that the relative proportion of synthesis does not change significantly during the developmental period that encompasses the blastocyst stage and early implantation as represented by the in vitro hatching, attachment and outgrowth of the blastocyst. Data on the characteristics of growth and culture of the outgrowths is also presented.