BIOKINETICS OF TRITIUM INCORPORATION INTO THE TISSUES OF RATS DURING CONTINUOUS INGESTION OF TRITIATED WATER OR TRITIUM-LABELED FOOD

Wistar strain male rats were continuously giventritiated water or tritiated wheat as drinking water orfood for 70 days.During the ingestion,the tritium in-corporation into rat tissues was examined in both wetand dry samples of liver,kidney,testis and blood.Theconcentration of organically bound tritium（OBT）indry tissues of rats exposed to tritiated water（HTO）andH-food（tritiated wheat）attained an equilibriumwithin 2-3 weeks after the exposure.The concentra-tion of OBT in dry tissues of rats exposed to HTO al-so reached an equilibrium within 3-4 weeks after theexposure.However,rats exposed toH-food,exceptfor the liver,such an equilibrium state was not reachedin other tissues and the OBT concentrations increasedgradually throughout the exposure.The relative con-centrations of totalH and OBT at the end of thechronic ingestion ofH food（70 day）,expressed inpercentages of the total activity were 1 and 9 timeshigher than those in rats exposed to HTO,respectively.In both groups,OBT as well as totalHwas almost uniformly distributed among the tissuesexamined.