Protein production by cultures established from Day-14-16 sheep and pig conceptuses.

Primary cell cultures were established from cells derived from dissociated Day-14 and -16 sheep and pig blastocysts. The appearance of cells in culture from both species was similar. Cultures contained a variety of cells with distinct morphologies, some were small and compact and formed clumps and multiple layers while others were large, flat and formed a monolayer. Within 4 h of culturing small floating fluid-filled spheres of cells were observed in the medium; some of these increased in size to greater than 1 cm diameter over 1-2 weeks. In addition, fluid-filled domes of cells arose from the underlying monolayer. Contractile cells became evident after about 8 days and some became organized into large patches of contracting tissue. Two-dimensional polyacrylamide gel electrophoresis and fluorography were performed on proteins released into the medium by confluent monolayers, floating spheres and floating cells that failed to attach during the first 24 h. All cultures produced as major products proteins with electrophoretic mobilities identical to certain fetal plasma proteins. In general, cultures did not produce proteins characteristic of short-term cultures of whole conceptuses harvested at Days 14-16. In cultures established from sheep blastocysts only the cells that failed to attach produced ovine trophoblast protein-1, a major polypeptide produced by the trophectoderm of the sheep conceptus between Days 13 and 21 of pregnancy.