Retention of intratracheally instilled and ingested tetravalent and pentavalent vanadium in the rat.

The retention, subcellular distribution in the liver, kidneys and lungs and binding of vanadium in the rat were investigated at 3 h, 1 d and 12 d after intratracheal instillation of 200 ng/kg body weight of 48V-labelled pentavalent and tetravalent vanadium. The metabolic patterns of both chemical forms of vanadium were similar. The lungs, liver, kidneys, bone, testes and spleen are the target tissues at risk, vanadium being removed from them with time at different rates. Pulmonary vanadium clearance was initially rapid - 80-85% of the 48V was removed within 3 h. At 12 d about 2% of the element was still present in the lung. Intracellularly, the major part of liver, kidney and lung vanadium was present in the nuclear fraction (30-40% of the homogenate), followed by cytosol and mitochondrial fractions. Gel filtration chromatography of the lung cytosol showed two biochemical pools of vanadium: the first corresponding to protein bound vanadium, which may be involved in the long-term accumulation of the element in the lung, the second pool representing a diffusible vanadium form. The retention of the tetravalent and pentavalent vanadium forms was also investigated 1 d after oral administration. No obvious differences were observed in the distribution pattern of 48V in the tissues, the retention factor being higher by two orders of magnitude in comparison with the intratracheally instilled animals. These findings suggest that the metabolic pathways of tetravalent and pentavalent vanadium are independent of the route of vanadium exposure.