CULTURE OF BOVINE EMBRYOS TO THE BLASTOCYST STAGE USING BUFFALO RAT-LIVER (BRL) CELLS

A comparison was made between the development of in vitro matured and fertilized bovine oocytes in co-culture with bovine oviduct epithelial (BOE) cells or with Buffalo rat liver (BRL) cells. Both cell types su pported development from the 1-cell to the blastocyst stage with equal efficiencies (4.4% for BRL cells, 4.0% for BOE cells). Medium conditi oned by either cell type supported development to the blastocyst stage as efficiently as co-cultures (6.4 and 7.3% blastocysts for BOE and B RL conditioned medium, respectively). A higher percentage of blastocys t development was found when embryos were cultured closely apposed in small drops of BRL-conditioned medium compared with larger volumes (20 .5 versus 7.0%). The ability of BRL-conditioned medium to support embr yonic development was dependent on the duration of the conditioning pe riod (optimum 24 to 48 h), and was not lost when the medium was stored at -20 degrees C for extended periods. The effects were independent o f the conditions used to promote maturation in vitro and the procedure for fertilization. With 2 different methods to produce embryos in cul ture, both the BRL cell co-culture and BRL-conditioned medium in micro drops supported embryo development to the blastocyst stage. The use of the BRL cell line reduces the variability associated with primary BOE cell cultures.