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Inhalation of 181W Labeled Tungstic Oxide by Six Beagle Dogs

1975; Lippincott Williams & Wilkins; Volume: 28; Issue: 6 Linguagem: Inglês

10.1097/00004032-197506000-00010

1538-5159

Roger Aamodt,

Inhalation and Respiratory Drug Delivery

Six purebred beagle dogs were exposed to 1.9–8 μCi of 181WO3 by nose only inhalation. The aerosol had an activity median aerodynamic diameter of 0.70 μm and a geometric standard deviation of 1.5. The activity deposited in the respiratory tract of each animal was estimated by three independent techniques. Retention and excretion were measured over 165 days. Following inhalation, 60% of the inhaled activity was deposited in the respiratory tract. Of this, about half was located, by gamma ray spectroscopy, in the lower portion of the tracheobronchial compartment and in the pulmonary compartment. Removal of the inhaled activity from the body was quite rapid. Partial body retention was determined from in-vivo gamma counting over the lung area and over the posterior portion of the dog's body. Whole-body retention was also estimated by subtracting the excreted activity from the inhaled activity at various times. The following retention patterns were determined, where t is the time in days: Lung position R = 0.69 e−(0.693/0.171)t + 0.23 e−(0.693/0.856)t + 0.05 e−(693/6.3)t + 0.03 e−(0.693/99)t Visceral position R = 0.94 e−(0.693/0.357)t + 0.04 e−(0.693/6.3)t + 0.02 e−(0.693/139)t Excreta collection R = 0.90 e−(0.693/0.603)t + 0.06 e−(0.693/5.8)t + 0.04 e−(0.693/63)t. The ratio of cumulative urinary excretion to cumulative fecal excretion for 165 days ranged from 0.57 to 1.8. This variation may have been related to differences in the clearance patterns of the individual dogs. Blood measurements indicated that the inhaled tungstic oxide entered the blood quite soon after inhalation and was rapidly removed. Measurements of selected organ and tissue samples at sacrifice (165 days post-inhalation) showed the highest concentration of tungsten in lung and kidney. Bane, gall bladder, liver and spleen were all about a factor of ten less than the lung, while the remaining organs decreased in the order: testes, pancreas, large intestine, small intestine, diaphragm, stomach, heart, and skeletal muscle. In terms of total organ burdens; most of the activity was found in bone (37%), lung (31%), kidney (15%), liver (9.7%), and skeletal muscle (5.7%). Body burdens calculated from organ and tissue burdens were in good agreement with in vivo gamma measurements at sacrifice.