Retention and tissue binding of titanium in the rat

Biokinetic models for group IVB elements

The International Commission on Radiological Protection (ICRP) is updating its biokinetic models in a series of reports titled Occupational Intakes of Radionuclides (OIR series). This paper provides an overview of biokinetic data for the group IVB elements hafnium (Hf) and titanium (Ti), compares these data with findings for the more extensively studied Group IVB element zirconium (Zr), and proposes biokinetic models for systemic Hf and Ti for use in the OIR series. The biokinetic model for systemic Zr adopted in OIR Part 2 (ICRP, 2016a) is proposed for application to Hf in view of the nearly identical chemical and physical properties of these two elements, their closely similar behavior in the environment, and their nearly identical biokinetic properties suggested by available comparative data. The model structure applied to Zr and Hf is also applied to Ti, but a separate set of transfer coefficients is proposed for Ti.

“In Vitro” Comparative Immune Effects of Different Titanium Compounds

Exposure to Ti compounds is today an occupational and environmental health hazard. Object of this study was to determine “in vitro” effects of different Ti salts on cultured human peripheral blood mononuclear cells (PBMC) proliferation and cytokine release. 10−4 and 10−7 M Ti compounds did not modify spontaneous PBMC proliferation. Ti dioxide (a biocompatible material and sunscreen component) did not exert effects on phytoemagglutinin (PHA) stimulated PBMC proliferation and on PHA stimulated IFN-γ and TNF-α release from PBMC. On the other hand, 10−4 M Ti oxalate (with wide industrial applications) and Ti ascorbate (used mainly in agriculture) inhibited about 70 % the PHA stimulated PBMC proliferation; both these Ti compounds at 10−4 and 10−7 M concentrations significantly inhibited TNF-α release, while only Ti oxalate inhibited that of IFN-γ. Titanocene (used in chemotherapy) did not exert effects on PBMC proliferation but markedly inhibited IFN-γ and TNF-α release. On the whole, this study demonstrates that Ti dioxide is not immunotoxic; Ti oxalate shows marked immunotoxicity; titanocene exerts selective toxicity on cytokine release but not on PBMC proliferation, while Ti ascorbate affects TNF-α release from PBMC but not IFN-γ release. In conclusion, these data show that immunotoxicity of Ti depends on speciation.

Identification of titanium in human tissues: probable role in pathologic processes

Six cases of titanium dioxide exposure involving lung, skin, and synovium are described, with a review of the literature. The patients, four men and two women, were between the ages of 22 and 65 years. The pulmonary changes were characterized by fibrosis and numerous macrophages with abundant deposition of a black pigment. Adjacent areas of bronchopneumonia were also observed. In the skin a severe necrotizing lesion involving the subcutaneous tissue with extension to the muscle was observed in one case and a nonspecific inflammatory response was observed in another; both cases showed abundant black pigment deposition. Electron microscopy and energy dispersive x-ray analysis demonstrated the presence of large quantities of titanium in the pigment granules. There may be a combination of black pigment deposition and fibrosis, necrosis, or a xanthomatous or granulomatous reaction, that, together with negative results on special staining and culture studies for organisms, should raise the suspicion of titanium-associated injury and prompt the study of the affected tissues by x-ray analysis for positive identification.

Organ distribution and pharmacokinetics of titanium after treatment with titanocene dichloride

The pharmacokinetics and organ distribution of titanium (Ti) were analyzed at various intervals up to 96 h after a single i.p. injection of a therapeutic dose of the antitumor agent titanocene dichloride (TDC, 60 mg/kg) by use of flameless atomic absorption spectroscopy in dried organ specimens. Highest organ concentrations were found in the liver and the intestine where 80-90 mg Ti/kg dry weight were accumulated at 24 and 48 h, corresponding to liver/blood and intestine/blood ratios of 8-9. However, at no time point after the TDC application, the Ti concentrations in brain tissue exceeded those of control animals. In solid tumors growing subcutaneously in mice, increasing amounts of Ti were found during the course of the experiment, reaching concentrations between 10 and 15 mg Ti/kg at 24 and 96 h after single i.p. application of TDC. These results confirm a typical pattern of organ distribution of Ti-containing metabolites of TDC, which clearly differs from that observed for vanadium after application of vanadocene dichloride or for platinum after treatment with cisplatin.