title: Cadmium effect on zinc metabolism in human trophoblast cells: involvement of cadmium-induced metallothionein.
abstract: Isolated trophoblast cells from human placenta at term were used to investigate the effect of cadmium exposure on the placental transport of zinc. Cells were exposed to cadmium acetate (0-2 microM) for 18 h. These concentrations were found to be non-cytotoxic as determined by protein recovery and the leakage of lactate dehydrogenase. Primary trophoblast cultures showed a cadmium-dependent increase in metallothionein content. After incubation with 65Zn for different times 65Zn contents were compared between control and cadmium-exposed cells. Zinc uptake by the cells after cadmium pre-exposure was increased in a cadmium dose-dependent manner. The additional amount of zinc that was taken up by the cadmium pre-exposed cells with respect to the control cells remained constant during a 30-min incubation of the same cells in a metal-free medium. The cytosol of cadmium-exposed cells showed a higher content of zinc than that of control cells. Most of the zinc in the cytosol is in the metallothionein fraction. We have thus demonstrated that cadmium-induced metallothionein binds zinc in the trophoblast, making this essential element less available to the fetal circulation.
authors.affiliation: Department of Biochemistry Research, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Torreblanca
authors.forename: J
authors.initials: J
authors.lastname: Del Ramo
authors.forename: B
authors.initials: B
authors.lastname: Sarkar
mesh_terms: D002104:Cadmium / Q000494:pharmacology*; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008668:Metallothionein / Q000096:biosynthesis* / Q000378:metabolism; D010920:Placenta / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D015032:Zinc / Q000378:metabolism*
chemical_list: D002104:Cadmium; D008668:Metallothionein; D007770:L-Lactate Dehydrogenase; D015032:Zinc