Effects of intrauterine devices on nuclear deoxyribonucleic acid metabolism in rabbit blastocysts: an...

A metabolic parameter, DNA synthesis, was measured in rabbit blastocysts exposed to Silastic intrauterine devices (IUDs) and compared with those without IUD exposure. Autoradiographic detection of 3H-thymidine uptake showed that the IUD-exposed blastocysts contained fewer labeled cells than their IUD-free equivalents. The depressed DNA synthesis may be caused by either a block in the cell cycle or a block in DNA synthesis itself. Either way, the result could be consistent with the observation that embryo deaths occur at all growth stages, preimplantation, during implantation, and postimplantation.