The Accumulation and Metabolism Characteristics of Rare Earth Elements in Sprague-Dawley Rats

The current study aims to investigate the influence of five rare earth elements (REEs) (i.e., lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), and gadolinium (Gd)) on the growth of Sprague-Dawley (SD) rats, and to explore the accumulation characteristics of REEs in tissues and organs with different doses as well as the detoxification and elimination of high-dose REEs. Fifty healthy male SD rats (140~160 g) were randomly divided into five groups and four of them were given gavage of sodium citrate solution with REEs in different doses, one of which was the control group. Hair, blood, and bone samples along with specific viscera tissue samples from the spleen and the liver were collected for detection of REEs by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Treated rats expressed higher concentrations of REEs in the bones, the liver, and spleen samples than the control group (P < 0.05). Few differences were found in relative abundance of La, Ce, Pr, Nd, and Gd in the hair and the liver samples, although different administration doses were given. The relative abundance of Ce in bone samples was significantly lower in the low-dose group and control group, whereas the relative abundance of La and Pr in the bone samples were highest among all groups. Although in the REEs solution, which was given to rats in high-dose group, the La element had a higher relative abundance than Ce element, it ended up with higher Ce element relative abundance than La element in the spleen samples. REEs had a hormetic effect on body weight gain of SD rats. The accumulation of the measured REEs were reversible to low concentrations in the blood and hair, but non-reversible in the bones, the spleen, and the liver. Different tissues and organs can selectively absorb and accumulate REEs. Further inter-disciplinary studies about REEs are urgently needed to identify their toxic effects on both ecosystems and organisms.