Comet Assay Evaluation of Lanthanum Nitrate DNA Damage in C57-ras Transgenic Mice

Due to the wide application of rare-earth elements (REEs) in the last decades, lanthanum has increasingly entered the environment and has gradually accumulated in the human body through the food chain. Lanthanum is worth paying attention in terms of food safety. Although the genotoxicity of lanthanum has been studied in vitro, data on its DNA damage in vivo rodent are limited, moreover, which have also presented some controversy. This study aimed to conduct an in vivo rodent alkaline comet assay, and as a companion test to the lanthanum nitrate carcinogenicity test. We conducted an oral gavage experiment for 180 days (26 weeks) to test for the persistence of DNA damage of long-term low-dose accumulation of lanthanum nitrate (12.5, 25, and 50 mg/kg body weight), in F1 hybrid C57-ras transgenic mice (CB6F1) by using alkaline comet assay in the blood and liver. The comet assay revealed that all the tested concentrations of lanthanum nitrate did not induce DNA damage in any of the tissues investigated, whereas DNA damage was induced in the positive control group. These results could indicate that lanthanum nitrate can accumulate in tissues and organs of the mice after exposure, and does not possess DNA damage in C57-ras transgenic mice after repeated treatments at oral doses up to 50 mg/kg·BW for 26 weeks; also, it did not cause pathological changes in the liver of the mice.