Bioavailability of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to the prairie vole (Microtus ochrogaster)

Concerns have been raised over potential bioavailability and biotransfer of energetic materials such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The present study assessed plant-incorporated [14C]RDX and plant-derived [14C]RDX-metabolite ingestion by the prairie vole (Microtus ochrogaster). The animals were fed labeled chow (maximum, < or =10 g/d) for 5 or 7 d, followed by a 6- or 4-d chase period. More than 95% of all label presented was recovered in the summed excreta, with 74% of this in the fecal nonabsorbed bulk. Greater than 20% of the presented [14C]RDX and plant-derived [14C]RDX metabolites were absorbed by the animals' digestive tracts. These materials were either metabolized to (14)CO2 (8-10% of the total label) or removed as nitrogenous waste through the kidneys (10-14%). Both 14C-urine and (14)CO2 excretion continued after the feces cleared, indicating ongoing metabolism of the labeled material. Approximately 4% was retained within the tissues at death, with the highest total activity in the liver and the highest specific activity in the testes. Other labeled tissues included the lung, heart, brain, spleen, skeletal muscle, bone, and pancreas. All these tissues containing [14C]RDX-derived materials are available to subsequent predators, indicating a potential for transfer to a higher trophic level.