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 epithelial cells (BOEC) in a defined medium which was used as a basic culture 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 addition 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 in 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 morula stage after the addition of TGF-beta 1 beta 2 only, or the addition 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 from the proportions obtained when embryos were cultured in groups, but were significantly (P < 0.005) lower than the proportions obtained when embryos were cultured in groups on BOEC monolayers. Arachidonic acid (50 ng mL-1), beta-mercaptoethanol (10 microM) and glutathione (10-1000 microM) 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 these embryotrophic substances (2.2-6.2%).