Cumulative labeling indices in epithelial cell populations of the respiratory tract after exposure to ozone at low concentrations.
Male Sprague-Dawley and F344 rats were exposed to concentrations of 0.12 ppm of ozone for 12 hr a night or for 24 hr a day, to 0.24 ppm for 24 hr a day, and to 0.36 ppm for 8 hr a night. Cumulative labeling indices were measured during the first and the third week of exposure in the terminal bronchioles, the large intrapulmonary airways, the trachea, and the anterior nasal passages. The most sensitive indicator for exposure to ozone after a 1-week exposure was an increased labeling index in the epithelium lining the terminal bronchioles. Sprague-Dawley and F-344 rats were equally sensitive to ozone. In the large intrapulmonary airways and in the maxillar turbinates, an increased cumulative labeling index was observed only at the highest dose (concentration x time). During the third week of exposure, no increases in labeling index were found in the large intrapulmonary airways and terminal bronchioles, whereas in the nasal passages the highest ozone concentration continued to elicit a proliferative response. Animals were also exposed for 1 week to ozone and then allowed to recover in air for another week. Renewed exposure to ozone produced a smaller, but still significant, increase in the labeling index compared to that in animals exposed to ozone for the first time. It was concluded that the determination of the cumulative labeling index in the terminal bronchioles may serve as a method to explore dose and time effects of such concentrations of ozone as may be encountered in heavily polluted urban environments.
Rajini
P
P
Institute of Toxicology and Environmental Health, University of California, Davis 95616.
Witschi
H
H
D000393:Air Pollutants / Q000633:toxicity; D000704:Analysis of Variance; D000818:Animals; D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009297:Nasal Mucosa / Q000187:drug effects* / Q000378:metabolism; D010126:Ozone / Q000008:administration & dosage / Q000633:toxicity*; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D000393:Air Pollutants; D010126:Ozone