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DYNAMIC ENVIRONMENTAL CYCLING OF HTO/HT/OBT

Objective

THE RESEARCH PROJECT AIMS AT DEFINING THE TRANSFER AND METABOLISM OF DIFFERENT FORMS OF TRITIUM IN MAMMALS IN ORDER TO DETERMINE UNDER WHICH CONDITIONS ORGANICALLY BOUND TRITIUM (OBT) WOULD CONTRIBUTE TO ITS TRANSFER IN THE ENVIRONMENT AND TO EXPOSURE OF MAN. IT ALSO STUDIES THE UPTAKE AND METABOLISM OF GASEOUS FORMS OF TRITIUM AND INCORPORATES A PILOT PROJECT ON CARBON-14. THE WORK WILL BE CARRIED OUT IN CLOSE COOPERATION BETWEEN THE RADIOBIOLOGICAL DEPARTMENT OF THE SCK-CEN AT MOL AND THE LABORATORY OF ANIMAL PHYSIOLOGY OF THE LANDBOUWHOGESCHOOL AT WAGENINGEN, INVOLVING REGULAR CONSULTATIONS AND COORDINATED DETAILED EXPERIMENTAL PLANNING, EXCHANGE OF MATERIAL (E.G. OF OBT LABELED FOOD, OF EXPERIMENTAL SAMPLES FOR ANALYSIS) AND COMMON DEVELOPMENT OF METHODS (ANALYSIS OF OBT IN TISSUES, MATHEMATICAL MODELS).
Organically bound tritium (OBT) in foodstuffs may be incorporated directly into the organic compounds of various organs and tissues of animals and man. The fraction of OBT which is incorporated, the residence time of the tritiated organic compounds and their location are important parameters for the determination of the radiation hazard of environmental tritium to man. Quantitative data for these parameters which can be used in the model developed to describe the kinetics of tritium in the human body.

Organically bound tritium (OBT) in foodstuffs may be incorporated directly into the organic compounds of various organs and tissues of animals and man. The fraction of OBT which is incorporated, the residence time of the tritiated organic compounds and their location are important parameters for the determination of the radiation hazard of environmental tritium to man.
Quantitative data are being obtained for these parameters which are to be used in the model developed to describe the kinetics of tritium in the human body. The metabolism of tritium gas (HT) will be investigated by the direct introduction of HT into animals.
DURING THE PREVIOUS CONTRACT, EXPERIMENTS WERE CARRIED OUT WITH MINI-GOATS AT THE LABORATORY OF ANIMAL PHYSIOLOGY AT WAGENINGEN. THESE ANIMALS WERE GIVEN OBT LABELED HAY THROUGH A RUMEN FISTULA FOR A PERIOD OF BETWEEN 150 AND 200 DAYS, AND TRANSFER INTO MILK AND INTO THE OFFSPRING AS WELL AS THE REPLACEMENT OF TRITIUM IN THE OFFSPRING WAS FOLLOWED. SOME OF THE MATERIAL OBTAINED FROM THESE EXPERIMENTS WILL BE FURTHER ANALYSED BY COLUMN CHROMATOGRAPHY TO INVESTIGATE OBT CONTENT IN DIFFERENT ORGANS AND COMPOUNDS (PROTEINS, DIFFERENT LIPID CONSTITUENTS ...) IN ORDER TO DEFINE THE SOURCES OF LONG-TERM RETENTION OF OBT IN BOTH YOUNG AND ADULT ANIMALS. THESE INVESTIGATIONS WILL BE CARRIED OUT IN PARALLEL WITH SIMILAR ONES ON MINIPIGS AT THE DEPARTMENT OF RADIOBIOLOGY AT MOL. AUTORADIOGRAPHIC STUDIES WILL ATTEMPT TO DEFINE WHICH SITES OF DEPOSITION OF OBT DURING IN UTERO AND NEONATAL EXPOSURE COULD LEAD TO CELL DAMAGE. SIMILAR EXPERIMENTS AFTER LONG-TERM FEEDING OF OBT WILL ALSO BE CARRIED OUT IN ADULT MINIGOATS IN ORDER TO DETERMINE TRANSFER FACTORS, DISTRIBUTION AND RESIDENCE TIME OF OBT. THE RESULTS OBTAINED IN MINIGOATS SO FAR, STRONGLY INDICATE THAT IMPORTANT DIFFERENCES EXIST BETWEEN YOUNG AND ADULT ANIMALS, PARTICULARLY WITH REGARD TO RESIDENCE TIME OF OBT. THESE EXPERIMENTS WHICH AIM TO ASSESS RISKS FROM QUASI-CONTINUOUS INGESTION OF OBT WILL BE COMPLETED BY STUDIES ON THE BEHAVIOUR OF OBT AFTER A SINGLE DOSE SIMULATING THE CONDITIONS AFTER AN ACCIDENT. THE INCORPORATION OF INDIVIDUAL TYPES OF OBT EXPOSURE WILL BE STUDIED BY GIVING THE MINIGOATS SEPARETELY OBT LABELED PROTEINS AND LIPIDS ISOLATED FROM TRITIATED MILK POWDER. IN ORDER TO SEARCH FOR INDICATORS WHICH WOULD ALLOW THE DETERMINATION OF EXTENT AND AGE OF A CONTAMINATION WITH OBT IN MAN, SAMPLES OF SERUM (PROTEINS, LIPIDS), URINE (UREA, URIC ACID, CREATININE) IN ADDITION TO MILK WILL BE ASSAYED IN RELATION TO MODE OF EXPOSURE TO OBT. MODELS WILL BE DEVELOPED TO ANALYSE THE DATA OBTAINED FROM THE SHORT AND LONG-TERM FEEDING EXPERIMENTS. BY COMPARING THESE MODELS WITH THOSE OBTAINED FROM THE DATA ON MONOGASTRIC MINIPIGS AT MOL, PREDICTION AND EXTRAPOLATION OF THE BEHAVIOUR OF OBT TO MAN SHOULD BECOME POSSIBLE. FOLLOWING PRELIMINARY STUDIES ON CONVERSION OF TH AND CH3T IN RODENTS CARRIED OUT IN MOL, THESE GASES WILL BE INTRODUCED DIRECTLY INTO THE STOMACH OR THE DUODENUM OF MINIGOATS, AND THEIR CONVERSION TO TRITIUM WATER AND OBT WILL BE FOLLOWED. PILOT STUDIES ON THE CONVERSION OF BICARBONATE AND OF ORGANICALLY LABELED CARBON-14 WILL BE CARRIED OUT ON PREGNANT MINIGOATS IN ORDER TO ANALYSE THE LONG-TERM BEHAVIOUR OF THIS RADIONUCLIDE.
THE EXPERIMENTS AT THE LABORATORY OF ANIMAL PHYSIOLOGY WILL BE CARRIED OUT IN CLOSE COOPERATION WITH THOSE AT THE DEPARTMENT OF RADIOBIOLOGY IN MOL.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

LANDBOUWHOGESCHOOL
Address
Salverdaplein 10
Wageningen
Netherlands