Developmental responses of 2-cell embryos to oxygen tension and bovine serum albumin in Wistar rats.

To improve rat embryo culture conditions, responses of Wistar 2-cell embryos from 2 breeders to oxygen tension (5 vs 20%) and bovine serum albumin (BSA) (0 vs 3 mg/ml) were examined using rat 1-cell embryo culture medium (mR1ECM). Supplementation of 3 mg/ml BSA significantly stimulated and accelerated development to the blastocyst and expanded blastocyst stages during 72 and 96 h culture, while reduced oxygen tension stimulated cell division. Fetus development after transfer of blastocysts obtained from 72 h culture under 5% O2 with BSA was significantly higher than those cultured under atmospheric oxygen without BSA. However, the nuclear numbers of in vitro cultured blastocysts and fetus development after embryo transfer were still significantly lower than in vivo developed blastocysts, indicating the current culture condition is still suboptimal.