Culture of rabbit zygotes into blastocysts in protein-free medium with one to twenty per cent oxygen

Embryos were collected from superovulated Dutch rabbits 19 h after injection of LH and insemination. The embryos were at the one-cell stage at that time and those judged to be normal by the absence of granular cytoplasm and regular shape were distributed randomly within donors into culture dishes containing 500 μl of a macromolecule-free medium consisting of RPMI-1640 and low glucose Dulbecco's modified Eagle's medium, 1:1, without a cover of oil. In Expt 1, O 2 concentrations of 5, 10 and 15%, with 5% CO 2 plus 90, 85 and 80% N 2 , respectively, were tested