The Clearance of Little Cigar Smoke Particles in the Lower Respiratory Tracts of Sprague Dawley Rats
Anthony S. Wexler, KAISEN LIN,
University of California, Davis Abstract Number: 109
Working Group: Health-Related Aerosols
AbstractLittle cigars are harmful tobacco products that have gained popularity among adolescents. In our previous study, we investigated the deposition patterns of little cigar smoke in the lower respiratory tracts of Sprague Dawley rats. Particle clearance after exposure is an essential factor influencing the actual particle uptake by recipients, which significantly impacts disease development. Differences in particle sizes and properties result in considerable variations in clearance rates within recipients' respiratory tracts. Consequently, predicting the clearance rate of little cigar particles in respiratory tracts is challenging, warranting experimentation with animal models. Our previous study indicated slow clearance of little cigar smoke particles in the lower respiratory tracts of Sprague Dawley rats, which was much slower than that reported in the literature. Additionally, a lobe-dependent deposition pattern was observed. Specifically, particles were more likely to deposit in the left and right caudal lobes than in other lung regions. We hypothesize that particle clearance kinetics may also vary among different lobes.
In this study, we exposed 12-week-old female Sprague Dawley rats to little cigar smoke for 2 hours per day over two days. Rats were sacrificed on Day 0, 1, 7, and 21 post-exposure, and their lungs were separated to collect individual lobes. Lung tissues were acid-digested and subsequently analyzed via ICP-MS. Chromium (Cr) levels, serving as a tracer of smoke particles, were quantified in samples. Lobe-specific particle clearance rates were calculated based on the changes in Cr levels over time. This study's results will provide essential information on the clearance rate of little cigar smoke particles after inhalation and deposition in rats' lower respiratory tracts. Animal study results will be compared with those predicted by the MPPD model.