THE FATE OF INTRAGASTRICALLY OR INTRATRACHEALLY ADMINISTERED OR INHALED VANADIUM-48 OXYDICHLORIDE IN JUVENILE AND MATURE RATS
Abstract
Vanadium levels in the atmosphere have been rising over the last two decades. The largest increases have been in industrialized high population areas of the United States. The major mode of entry into the body for atmospheric vanadium is through the respiratory tracts. The effects of vanadium on the respiratory tract have been documented by many researchers. However, the literature does not contain, quantitative information on the absorption and subsequent distribution of inhaled vanadium. The current study was initiated to add quantitative data that may be useful in the formulation of environmental standards for atmospheric vanadium. The objective of this research was to investigate the absorption of soluble vanadium (vanadium oxydichloride) from the respiratory and digestive tracts of male Sprague Dawley rats of two ages. On each of the experiment, a new group of ten rats (five juvenile, five mature) were administered vanadium oxydichloride (labeled with vanadium-48) by intragastric injection, intratracheal injection, or inhalation exposure. Six replicates of each administration mode were performed. Immediately following vanadium administration, the animals were placed in individual metabolism cages enabling collection of the urine and feces. The intragastric injections resulted in 0.76 (+OR-) 0.14 ug (20.1 (+OR-) 3.8 uCi) of vanadium deposited in the stomach. The average depositions in the respiratory tract were 1.0 (+OR-) 0.1 ug (5.3 (+OR-) 0.4 uCi) vanadium for the intratracheal injections and 6.0 (+OR-) 1.2 ug (2.0 (+OR-) 0.4 uCi) vanadium for the inhalation exposures. The activity median aerodynamic diameter, AMAD, for the aerosol exposures averaged 0.76 microns with a geometric standard deviation of 1.96. The animals were sacrificed at various times, 1/2, 2, 6, 24, or 96 hours post administration, and selected organs and tissues were removed and analyzed for their vanadium-48 content. The amount of vanadium-48 was determined using a large well NaI(Tl) crystal detection system. The absorption from the digestive tract was slight with 2.6% of the intragastrically administered dose appearing in the tissues of the body (minus the digestive tract) or in the urine at 4 days. The absorption from the lungs following intratracheal injection was rapid with approximately 51% of the administered dose remaining in the lungs at 30 minutes and 8.6% remaining at 4 days. The 0.76 micron AMAD aerosol generated for the inhalation administration favored deposition in the lungs and nasopharyngeal regions of the respiratory tract. As in the intratracheal administration, the vanadium absorption from the lungs following inhalation was rapid with 26.2% of the vanadium deposited in the respiratory tract remaining in the lungs at 30 minutes and 8.3% remaining at 4 days. The absorbed vanadium was distributed similarly throughout the body tissues independent of the point of entry. The urine and fecal values were used as indicators of systemic (absorbed) and unabsorbed vanadium, respectively. From this study, absorption values of 2.5% from the digestive tract and 80% from the lungs have been calculated and should be considered when calculating the potential body burden of vanadium from environmental exposures to soluble vanadium. In both the intratracheal injection and inhalation modes of administration, the mature animals retained a larger percentage (8.5%) of the administered dose in the lungs than the juvenile animals (3.7%). The juvenile animals initially had higher levels in the spleen but this difference disappeared at 4 days. The juvenile animals consistantly had femur vanadium levels that were 50 to 100% above those in the mature animals. All other tissues and excreta did not show differences attributable to the age of the experimental animals.
Degree
Ph.D.
Subject Area
Environmental science
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