Quantity and quality of embryos collected from mice passively immunized against estradiol

The objective of this study was to determine the effects of passive immunization against estradiol on the occurrence and timing of estrus, ovulation and fertilization rates and on early embryonic development in mice. Swiss Webster female mice were randomly assigned to one of the three treatment groups to be injected with 0.1 ml saline (control; n=15), 0.1 ml anti-estradiol antisera (high dose: n=17) or 0.1 ml antiestradiol antisera diluted 1:10 with saline (low dose; n=17) at seven weeks of age. Immediately after injection mice were placed with males and observed daily for the presence of vaginal plugs for 10 d. Three days after vaginal plugs were observed, mice were terminated and the uteri were removed and flushed to determine the number and quality of unfertilized ova and embryos. No differences were observed in the timing of vaginal plug formation, the proportion of mice with vaginal plugs, or the mean number of unfertilized ova or embryos collected from each treatment group. However, the proportion of excellent or good quality embryos was reduced in the high dosage treatment. It was concluded from this study that passive immunization of mice against estradiol did not increase the number of embryos obtained from mice and that a high dosage of antisera against estradiol reduced embryo quality. These results provide evidence that alterations in levels of estradiol may adversely affect embryonic development.