PLACENTAL TOXICOLOGY

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The placenta can be a site for specific toxic action compromising the growth and survival of the conceptus from birth until delivery, e.g,. cadmium can produce placental necrosis and fetal death in rodents and necrosis under perfusion conditions in the human placenta. During the past two years, we have extended the perfusion of human placentae to 24 hours and developed a 3-dimensional culture of trophoblast and a human endometrial culture model, which develops from isolated cells into glands and stroma covered by epithelium. Utilizing the perfused human placenta we have documented that zinc can protect against acute toxic effects of cadmium in the human placenta. In addition, the initial actions of cadmium appear to be on protein synthesis rather than ATP, since 31p NMR/MRI spectroscopy demonstrated no effect on ATP while hPL and hCG were decreased. Further studies demonstrated continuous monitoring of ATP demonstrated that the human placenta has the tremendous glycolytic capacity; however, once exhausted - ATP levels do fall; however, at that point if reoxygenation occurs, recovery of ATP is rapid and persistent. ATP levels have been found constant for period of 10 hours under normal perfusion conditions (longest period studied). Additional studies have demonstrated that the human placenta (both early and term) can metabolize retinoids, in particular isotretinoin (Accutane) to tretinoin. Such metabolism by the human placenta may partially account for the species differences between rodents and human concerning the teratogenicity of these agents. Also it was demonstrated that enteroviruses do not penetrate through he human term placenta even after 15 hours of exposure, when virus is found in maternal perfusate and placental specimens. The specific aims of this proposal are: 1. Determine the relationship between cadmium (Cd) toxicity and modifiers of that toxicity (zinc, selenium and calcium) on known placental function and morphology, 2. Determine if the early trophoblast and its interaction with the human endometrium (Attachment/Invasion ("implantation") is responsive to Cd and Ru486, 3. Since Cd induces metallothionein (MT), determine the regulation of induction of MT(I/II) and its relationship to protection against Cd toxicity, and 4. Study placentae from pregnant nonsmokers and smokers (>30 cigarettes/day) using perfusion and then determine if heavy smokers are protected from the acute placental toxicity in vitro.