Tissue uptake and intracellular distribution of 140-lanthanum after oral intake by the rat.

The ability of lanthanum to stabilize hydroxyapatite against acid dissolution is well known. It is possible to use lanthanum to experimentally alter hard tissues in vivo and in vitro. It was, therefore, of interest to determine the tissue distribution of lanthanum following oral ingestion of a LaCl3 solution. Oral intake of 140-lanthanum (as LaCl3 in drinking water) in adult rats over a 3-d period was voluntary and amounted to 0.27 mmol LaCl3 per animal per day. The teeth sowed increases in 140-lanthanum uptake with time. Distribution of 140-lanthanum within the incisors of animals drinking the LaCl3 solution showed that the highest specific activity of 140-lanthanum was associated with the outer layer of the tooth (that portion exposed to the oral environment). The soft tissues, such as lung, kidney, and liver, maintained a constant 140-lanthanum concentration after the first day of intake. The intracellular distribution of 140-lanthanum was measured in liver, with the soluble fraction showing the highest content. No histological changes were observed in the rat tissues after 3 d of oral intake (0.27 mmol/d) of lanthanum.