Time-dependent variation in the biodistribution of C₆₀ in rats determined by liquid chromatography-tandem mass spectrometry.

We examined the biodistribution of C(60) in rats after tail vein administration using LC-MS/MS. C(60) was detected in various tissues, such as brain, kidneys, liver, lungs, and spleen of rats. On the other hand, no C(60) was found in blood. The highest C(60) concentration was observed in the lungs, followed by spleen, liver, kidneys, and brain. These results suggested that C(60) injected in the tail vein could be filtered by lung capillary vessels and accumulate in the lungs prior to being distributed to other tissues. Moreover, C(60) not being detected in the blood indicates that clearance of C(60) from the blood by filtration might effectively occur in the lungs. The time-dependent variation in the biodistribution of C(60) was evaluated. A time-dependent decrease in C(60) concentrations was observed in all tissues, except spleen. Moreover, a decreasing trend of C(60) levels differed among tissues, which could be due to differences in accumulation. These results suggest that unmodified C(60) and/or C(60) metabolites by metabolic enzymes could be excreted into feces and/or urine. In further studies, the metabolic and excretion pathways of C(60) should be evaluated to understand the toxicokinetics of C(60).