2-Week and 13-Week Inhalation Studies of Aerosolized Glycerol in Rats

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Abstract
The potential toxicity of aerosolized glycerol was studied by 2-wk and 13-wk nose-only inhalation exposures in Sprague-Dawley-derived (Cr1:CD) rats. In the first study, 10 ratslsedgroup received 10 nose-only exposures of 6 h/day for 2 wk over a 14-day period to mean aerosol concentrations of 0, 7.00 ± 0.08, 1.93 ± 0.123, or 3.91 ± 0.458 mg glycerol/l of filtered room air: Animals were observed for signs of toxicity twice daily, were weighed at 2– to 3-day intervals, and diet consumption was recorded at weekly intervals. All rats underwent complete necropsy, and designated tissues were weighed and examined histopathologically Blood was collected and analyzed for specific hematological and clinical chemistry parameters. The results of this study showed that rats exposed to 6-h nose-only inhalation for 70 days at all three concentrations of glycerol exhibited minimal to mild squamous metaplasia of the epithelium lining the base of the epiglottis. In a second study, 75 ratslsedgroup were exposed 6 h/day, 5 days/wk, for 13 consecutive weeks to mean aerosol concentrations of 0, 0.033 ± 0.0046, 0.167 ± 0.023, or 0.662 ± 0.085 mg glycerol/l of air: Clinical and postmortem evaluations similar to those described above for the 2-wk study were performed on all rats of the 12wk study. In addition, six randomly selected ratdsex from the 0.662 mg/l group and from the control group were killed separately for ultra-structural evaluation of the lungs. Minimal to mild squamous metaplasia of the epithelium lining the base of the epiglottis was observed only in rats exposed to 0.662 mg glycerol// of air for 13 wk. Ultrastructural examination of Clara cells did not provide evidence of proliferation of smooth endoplasmic reticulum in glycerol-exposed rats.