Titanium retention in mice

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.

Distribution of titanium and vanadium following repeated injection of high-dose salts

Titanium and its alloy of 6% aluminium and 4% vanadium are used extensively in orthopedic and dental surgery. However, in conditions of motion leading to wear, there is significant generation of wear products with deposition of black debris in the tissue. The questions remain as to how much of this debris is generated and to where it is transported. Previous studies have been hampered by low levels of detected elements giving values just above the background levels found in normal tissue and body fluids. The purpose of these experiments was to increase the body burden of titanium and vanadium by injecting larger doses of titanium and vanadium salts over an extended period of time. Each animal (Syrian hamster) received 100 micrograms of each element once a week for six weeks. The hamster was sacrificed on the seventh week and body fluids and tissue harvested. The results indicate that in the experimental animals there was transport of vanadium with levels above control in urine, plasma, liver, spleen, and the mineralized portion and organic portion of bone. Titanium had less transport but still showed levels in the experimental animals in plasma, kidney, liver, spleen, and both phases of bone above those in the control animals. Neither element was found above control levels in lung or red blood cells. The levels of titanium and vanadium in control bone were high, possibly indicating bone as a site for storage and accumulation of these elements when encountered in the activities of daily living.

Retention and tissue binding of titanium in the rat

The fate of a soluble form of titanium (Ti) was studied in rats injected intraperitoneally with 1 microgram of Ti per rat as [44Ti]ammonium oxalotitanate (IV). After 16 h the Ti concentration in all tissues tested was of the order of 0.5 ng/g wet weight. After 19 days the Ti concentration increased in most tissues, especially in spleen, femur and kidney. By this time 55 ng had been excreted both via urine and faeces and the Ti concentration in blood plasma (mainly associated with plasma proteins) was three times lower than at 16 h postinjection. Chromatographic separation of the day 19 liver cytosol showed the ability of biological macromolecules to incorporate Ti compounds. Ti-labelled 'titanic acid' and 'titanium phosphate' showed low solubility which was, however, higher in human serum than in water and sodium chloride solution. The chromatographic profiles of plasma from incubated human blood in vitro with [44Ti]titanium oxalate showed the capacity of plasma proteins to complex Ti compounds. The results indicated that the long retention of Ti in the body may be due to its ability to form biocomplexes with cellular constituents.