ABSTRACT
The clearance of sulfuric acid-introduced 35S from the upper and lower respiratory tracts of rats, guinea pigs and dogs was measured. Sulfuric acid was administered by instillation and by inhalation for each species. Clearance into the blood and gastrointestinal tract was measured along with determination of 35S remaining at the site of administration at sacrifice. Different rates of clearance from different sites within the dog lung were indicated with rates of clearance increasing with decreasing airway diameter. Half-times of clearance from all sites in the lung and for all species were from 2-9 min. There appeared to be some species differences, with clearance for dogs being slower than for guinea pigs, which was slower than for rats. Upper respiratory tract clearance was much slower than for lung and may not have been primarily by way of the blood. The data indicate that the clearance of sulfuric acid-introduced 35S in vivo is faster than previous studies in isolated perfused lungs had indicated. The results may be general for water soluble, ionized chemical species.
Subject(s)
Respiratory System/metabolism , Sulfuric Acids/metabolism , Aerosols , Animals , Dogs , Guinea Pigs , Half-Life , Lung/metabolism , Male , Rats , Rats, Inbred F344 , Species Specificity , Sulfur Radioisotopes , Sulfuric Acids/administration & dosage , Time FactorsABSTRACT
Tracheal mucous transport was measured using similar techniques in several species. One- to 10-microliter quantities of 99mTc-macroaggregated albumin (99mTc-MAA) were instilled via oral intubation in the distal trachea of rats, rabbits, and dogs. Tracheostomies were used for the instillation in guinea pigs. All animals were anesthetized with halothane for the instillation and allowed to recover immediately in restrainers. Clearance of the 99mTc-MAA in rats and guinea pigs was measured by a slit-collimated NaI scanner. In rabbits and dogs a series of gamma-camera scintiphotos were taken. Clearance was faster and more efficient in dogs than in the other species. No significant differences existed among the rats, rabbits, and guinea pigs in the percentages of the originally deposited material remaining at the instillation site after 1 h (P greater than 0.2). Mean values and standard deviations were 83 +/- 23%, 81 +/- 22% and 70 +/- 20% for rats, guinea pigs, and rabbits, respectively. However, in the dogs a mean of 14 +/- 12% remained at the original site of deposition after only 25 min indicating much more rapid clearance. Mean leading-edge velocities were 9.8 +/- 2.1 (SD) for dogs, 3.2 +/- 1.1 for rabbits, 2.7 +/- 1.4 for guinea pigs, and 1.9 +/- 0.7 mm/min for rats. Clearance patterns qualitatively among the species. In dogs the material moved as a few discrete boluses, whereas in the other species the activity spread toward the larynx. The relatively slow mucous transport of rats, rabbits, and guinea pigs could have important implications in inhalation toxicological studies.
