Blastocyst-endometrial interactions and protein synthesis during pre-implantation development in the pig studied in...

A co-culture technique is described for the study in vitro of interactions between elongated blastocyst tissue and endometrium in the pig. Culture conditions which were optimal for blastocyst protein synthesis were determined and tissue survival was assessed after 48 h in culture. A defined medium was adopted consisting of medium 199 supplemented with insulin and antibiotics. Blastocyst protein synthesis measured by labelled leucine incorporation was not enhanced by the addition of serum, suggesting either that it was not required for optimal protein synthesis ar that active substances of maternal (endometrial) origin were already adsorbed on to embryonic tissues. Endometrial explants co-cultured with blastocyst tissue enhanced blastocyst protein synthesis approximately fourfold when intrinsic protein synthesis was low, but had little effect if it was already high. Blastocyst explants in which protein synthesis was enhanced by co-culture with endometrium demonstrated an increased synthesis of prealbumin proteins with molecular weights of 25 000 to 30 000.