ZINC IS A POSSIBLE TOXIC CONTAMINANT OF SILICONE OIL IN MICRODROP CULTURES OF PREIMPLANTATION MOUSE EMBRYOS

A batch of silicone oil (dimethylpolysiloxane) is described which had differential effects on the development of 1- and 2-cell preimplantati on mouse embryos in vitro when used as a microdrop overlay over two cu lture media: CZB and KSOM. A high rate of development into blastocysts was observed when using CZB medium;in contrast, development was stron gly inhibited when KSOM was used, Other batches of silicone oil or par affin oil permitted development from the zygote to the blastocyst of a n outbred strain of mouse without arrest at the 2-cell stage. Our resu lts show that the higher concentrations of ethylenediaminetetraacetic acid (EDTA) and bovine serum albumin (BSA) in CZB medium, in compariso n with KSOM, protect against the toxic component in the oil, Observati on's also gave circumstantial evidence that the toxic component in the oil is zinc. The beneficial effect of including EDTA in a medium is u sually attributed to its chelating toxic metals introduced as impuriti es in other components of the medium. Our results now show that EDTA a lso protects against impurites in the oil overlay.