Comparative Biokinetics of Radiocarbon Ingested as Compounds or Foods in Rats

Abstract

The biokinetics of radiocarbon (¹⁴C) in rats continuously ingested in the forms of amino acids (glycine and leucine) or as foods (wheat and rapeseed) were examined and compared with each other. The differences in the biokinetics between ¹⁴C-amino acids and ¹⁴C-foods were observed in the excretion of ¹⁴C in feces and in the incorporation and retention of ¹⁴C in the rat tissues. At the 10 week of continuous ingestion of ¹⁴C-amino acids, the integrated activities of ¹⁴C in all the tissues were within 5% of the ingested activity. The integrated activities in each tissue coming from ¹⁴C-food ingestion were higher by a factor of more than 2 compared to those coming from ¹⁴C-amino acid ingestion. Radiation dose rates estimated at the 10 week showed that the dose rates to the individual tissues coming from ¹⁴C-food ingestion were 2-5 times higher than those coming from ¹⁴C-amino acid ingestion. The difference in the dose rate between ¹⁴C-amino acid and ¹⁴C-food was more significant in adipose tissue by a factor of 7-30.

Biokinetics of13C in the human body after oral administration of13C-labeled glucose as an index for the biokinetics of14C

“…Some animal data has been reported regarding the metabolism of 14 C incorporated into molecules of major nutrients and foods, e.g. glucose in sheep (Crout et al 1998); leucine, glycine, lysine, palmitic acid, oleic acid, glucose, and thymidine in rat (Takeda et al 1998); and 14 C-labeled wheat (Takeda et al 2009) and rapeseed (Takeda et al 2010) in rat. However, few studies have examined the metabolism of 14 C in component molecules of major nutrients in human, although human metabolic data of 14 C in specific molecules has been reported from pharmacological studies (Lappin and Garner 2004) and from actual diagnostic use (glycocholic acid and xylose; Gunnarsson et al 2007).…”