Inorganic elements in the tooth and bone tissues of rats bearing nickel acetate- and lead acetate-induced tumors

Biological effects of such metals as nickel and chromium alloys used as dental materials, particularly their metabolism and potential toxicity have not been well elucidated. Certain metallic materials are known to be toxic and arsenic, nickel, chromium and lead have been shown to have carcinogenic potential in laboratory animals. This study was performed to assess carcinogenicity and accumulation in tissues of metals in rats. Three-week old male F344/NSle rats were injected s. c. with 30 mg/kg of nickel acetate or 60 mg/kg of lead acetate weekly for 5 weeks after 2 weeks of acclimatization, and were followed by observation for 80 weeks. The group treated with lead acetate showed a greater incidence of tumor, compared with the nickel acetate-treated group. Teeth, femora, other bones and neoplastic tissue from tumor-bearing animals were subjected to elemental analysis by spectrophotometry and ICP. High concentrations of Pb were detected in the mandibula, femur and tumor tissue of rats with Pb-induced tumor. In rats with Ni-induced tumor, Ni was not demonstrable in the mandibula, maxilla or tumor tissue and detected in small quantities in the nasal bone and femur. Thus, Pb proved to be retained in tissue at the site of injection and also markedly accumulated in the tooth and femur as assessed 46 weeks after injections; whereas Ni was no longer detectable in tissue at the injection site, nor in tumor tissue but only small quantities in the said bones.