Induction of metallothionein in a human trophoblast cell line by cadmium and zinc.

The induction of metallothionein (MT) in a cell line derived from a malignant trophoblastic tumor (JAr cells) was demonstrated using the Cd/heme radioassay following exposure to Cd or Zn. Cd at an optimal concentration of 1 microM produced a 30-fold increase in MT following a 24 hr incubation. Induction by Cd was both time and dose dependent, with a significant increase in MT noted as early as 3 hr, with levels continuing to increase up to 24 hr. Zn was also quite effective in inducing MT synthesis in this cell line. Exposure to 80 microM Zn for 24 hr produced a 70-fold increase in MT. Although Cd was a more potent inducer of MT, exposure to Zn resulted in a greater magnitude of induction. The magnitude of MT induction in JAr cells was much greater than that seen in cultured trophoblasts from term chorion laeve. The degree of induction seen in this cell line makes it an interesting model for the study of MT's role in trophoblast function. MT induction in trophoblasts may reflect a protective mechanism against heavy metal toxicity and/or an integral aspect of normal zinc homeostasis.