ToxSci Advance Access originally published online on July 13, 2006
Toxicological Sciences 2006 93(2):400-410; doi:10.1093/toxsci/kfl059
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Published by Oxford University Press 2006.
Particle Deposition in Spontaneously Hypertensive Rats Exposed via Whole-Body Inhalation: Measured and Estimated Dose
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* Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599; Environmental Media Assessment Group, National Center for Environmental Assessment, MD B243-01, and Pulmonary Toxicology Branch, Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; and Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
Received April 20, 2006; accepted July 9, 2006
A plethora of epidemiological studies have shown that exposure to elevated levels of ambient particulate matter (PM) can lead to adverse health outcomes, including cardiopulmonary-related mortality. Subsequent animal toxicological studies have attempted to mimic these cardiovascular and respiratory responses, in order to better understand underlying mechanisms. However, it is difficult to quantitate the amount of PM deposited in rodent lungs following inhalation exposure, thus making fundamental dose-to-effect assessment and linkages to human responses problematic. To address this need, spontaneously hypertensive rats were exposed to an oil combustion–derived PM (HP12) via inhalation while being maintained in whole-body plethysmograph chambers. Rats were exposed 6 h/day to 13 mg/m3 of HP12 for 1 or 4 days. Immediately following the last exposure, rats were sacrificed and their tracheas and lung lobes harvested and separated for neutron activation analysis. Total lower respiratory tract deposition ranged from 20–60 µg to 89–139 µg for 1- and 4-day exposures, respectively. Deposition data were compared to default and rat-specific estimates provided by the Multiple Path Particle Deposition (MPPD) model, yielding model predictions that were < 33% of the measured dose. This study suggests that HP12 exposure decreased particle clearance, as the mass of HP12 in the lungs following a 4-day protocol was nearly four times that observed after a 1-day exposure. This work should improve the ability of risk assessors to extrapolate rat-to-human exposure concentrations on the basis of lung burdens and, thus, better relate inhaled doses and resultant toxicological effects.
Key Words: rat; particle; deposition.
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