COVERING EMBRYO CULTURES WITH MINERAL-OIL ALTERS EMBRYO GROWTH BY ACTING AS A SINK FOR AN EMBRYOTOXIC SUBSTANCE

Purpose: Assisted reproductive technologies, require the use of culture media for. gametes and embryos. Culture media and conditions intended for use in human in vitro fertilization are tested prior to else by evaluating their ability to support normal development of mouse embryos. Results: Development to blastocysts of two-cell mouse embryos Mins equivalent for embryos cultured in center well dishes alone (93 +/- 10%, mean +/- SD) and embryos cultured in center well dishes with ai I overlay of 1 mi of mineral oil (94 +/- 5%). In contrast, no development of two-cell-stage mouse embryos occurred in an embryotoxic medium when cultured in center well dishes. However , when this medium was covered with an overlay of mineral oil, development to blastocyst was no different than that of controls (96 +/- 5%). Similar results were found with cultures of one-cell-stage mouse embryos. Conclusion: These results indicate that in some cir circumstances the presence of mineral oil can significantly alter the outcome of embryo culture. Further, these results reinforce the necessity of directly testing the exact culture conditions to be used for assisted reproductive technologies.