Biokinetics of radiocarbon ingested as a food in rats

Biokinetics of radiocarbon (C) in rats during 14 wk of continuous ingestion of C-wheat was investigated to obtain the dosimetric data on organic C ingested as a food. After the start of continuous ingestion of C-wheat, the concentrations of C in both wet and dry tissues gradually increased and showed a tendency towards a steady-state condition for most of the tissues, except adipose tissue. The steady-state condition was observed at 10 wk in the majority of tissues, but was obtained at 3 wk in liver. The steady-state concentrations in wet tissues ranged from about 10% to 40%, and those in dry tissues ranged from about 80% to 100% of the concentration of C in the ingested food. The highest steady-state concentrations in both wet and dry tissues were observed in liver. When compared the concentrations among tissues at the end of 14 wk of continuous ingestion, adipose tissue was the highest in wet tissue and the lowest in dry tissue. From the concentrations of C in wet tissues at the 14th week, the radiation dose rates to individual tissues were estimated. The dose rates were different among the tissues. The highest dose rate was observed in adipose tissue. The next highest dose rates were found in liver and small intestine, while lower doses were measured in testis and lung. The differences in the dose rate among the tissues seemed to be mainly dependent on the variation in the organic content of each tissue.