Alveolar clearance in dogs after inhalation of an iron 59 oxide aerosol

¹ Departments of Radiation Biology and Pharmacology, University of Rochester, Rochester, New York

Six dogs each received two 60-min exposures, 6 months apart, to an aerosol of iron 59 oxide, having an average count median diameter of 0.09 µ and a geometric standard deviation of 1.8. The concentration of iron 59 in the inspired air ranged between 0.004–0.017 µc/liter. Lung measurements were made immediately after each exposure and up to 30 days postexposure. This procedure was followed in both initial and repeat exposures of each dog. A probe-type scintillation detector fitted with a focusing collimator was used to limit the measurements to specific respiratory tract positions on each dog. The biological half-time for alveolar clearance in the 12 studies ranged from 44 to 82 days with an average value of 62 days (sd 8.8 days). This consistency suggests the probability of a normal clearance rate and the possibility of its use as a functional test.