DISTRIBUTION OF VANADATE IN THE RAT FOLLOWING SUBCUTANEOUS AND ORAL ROUTES OF ADMINISTRATION

The distribution of radiolabeled vanadate (V-48) was studied in rats following subcutaneous or oral route of administration (1.8 mg V/kg). Measurements included: (1) tissue uptake and retention; (2) gastrointestinal (GI) absorption efficiency; and (3) the fraction of the dose eliminated via the urinary and the GI tracts during the study period. The vanadium content of tissues and excreta was determined by gamma spectroscopy. All tissues analyzed were found to have a measurable level of vanadium after 2 hours of its administration by subcutaneous route. Soft tissues and blood showed the maximal measured concentration of vanadium at 2 hours, while in the bone, the maximal concentration was recorded at 1 day posttreatment. The distribution of vanadium in each tissue could be described by a two-compartment model. Vanadium was cleared rapidly from the soft tissues and slowly from the bone. The elimination half-lives of vanadium ranged between 11 and 132 hours for soft tissues and 376 hours for the bone. During the first day, 48.6% of the dosage was eliminated in the urine and 8.0% in the feces. The GI uptake following gavage was approximately 4.2% of the dosage at 24 hours posttreatment. Vanadium absorbed from the GI tract was distributed among the major tissues and about 66% of the absorbed fraction was excreted in the urine after two weeks posttreatment.