ROLES OF GROWTH-FACTORS IN THE DEVELOPMENT OF BOVINE EMBRYOS FERTILIZED IN-VITRO AND CULTURED SINGLY IN A DEFINED MEDIUM

Bovine embryos at the 8- or 16-cell stage were cultured singly, or in groups (10-12 embryos), in the presence or absence of bovine oviduct e pithelial cells (BOEC) in a defined medium which was used as a basic c ulture medium. A higher (P < 0.05) proportion of 8-cell embryos (48.3- 50.8%) cultured singly developed beyond the 8-cell stage after the add ition of platelet-derived growth factor (PDGF)-AB (1 ng mL(-1)) only, or with PDGF-AB + basic fibroblast growth factor (bFGF; 1 ng mL(-1)) transforming growth factor (TGF)-beta(1) beta(2) (1 ng mL(-1)) than i n basic medium alone (30.3%). In contrast, a significantly (P < 0.02) higher percentage (62.6-65.8%) of 16-cell embryos developed to the mor ula stage after the addition of TGF-beta(1) beta(2) only, or the addit ion of TGF-beta(1) beta(2)+bFGF+PDGF-AB than in basic medium alone (30 .2%). These proportions were not significantly (P > 0.05) different fr om the proportions obtained when embryos were cultured in groups, but were significantly (P < 0.005) lower than the proportions obtained whe n embryos were cultured in groups on BOEC monolayers. Arachidonic acid (50 ng mL(-1)), beta-mercaptoethanol (10 mu M) and glutathione (10-10 00 mu M) Stimulated the development of 8-cell embryos in the presence of PDGF and TGF-beta(1) beta(2); blastocyst formation was observed for the first time in 8-cell embryos cultured singly in the presence of t hese embryotrophic substances (2.2-6.2%).