The biliary excretion of V was studied in bile duct-cannulated rats at various times after the i.v. administration of a single dose of 48V-labeled pentavalent V.The tissue disposition, hepatic intracellular distribution, and binding of 48V to plasma, bile, and liver components were also investigated.During the 1st 6 h after the injection of V, 0.9-30 μg/kg, <2% of the dose was excreted into the bile and ≤20% of V was eliminated in the urine.The bile flow was markedly decreased in rats cannulated 24 h after the injection of V (30 μg/kg), while higher doses produced signs of severe toxicity immediately after administration.Evidence was also obtained that a concentration gradient triggers the passage of V from plasma to the liver, where only a fractional amount becomes available for canalicular excretion, due to the extensive binding of the metal to organelles and other tissue ligands.