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.