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Increased susceptibility of hyperthyroid rats to ozone: early events and mechanisms.

Authors
Huffman-LJ; Beighley-CM; Frazer-DG; McKinney-WG; Porter-DW
Source
J Toxicol Environ Health, A 2006 Mar; 69(6):465-479
NIOSHTIC No.
20030026
Abstract
Previous studies demonstrated that ozone-induced lung damage and inflammation are much greater in hyperthyroid rats, compared to normal rats, at 18 h postexposure. The purpose of the present investigation was to study early events and mechanisms underlying the increased sensitivity to ozone in a hyperthyroid state. Specifically, the degree of lung epithelial cell barrier disruption, the antioxidant status of the extracellular lining fluid, and the release of inflammatory mediators were examined. To induce a hyperthyroid state, mature male Sprague-Dawley rats were implanted with time-release pellets containing thyroxine; control rats received placebo pellets. After 7 d, the animals were exposed to air or ozone (2 ppm, 3 h). Immediately following the end of the exposure, bronchoalveolar lavage (BAL) fluid and cells were harvested. BAL fluid albumin levels and total antioxidant status were examined. In addition, levels of prostaglandin E2 (PGE2), macrophage inflammatory protein (MIP)-2, MCP-1, and tumor necrosis factor (TNF)-alpha were determined in BAL fluid and in media samples following ex vivo culture of BAL cells harvested after in vivo inhalation exposures. The results of this study are consistent with the following hypotheses: (1) A marked increase in the permeability of the alveolar-capillary barrier is an early event following ozone exposure in a hyperthyroid state; however this does not appear to be due to overall changes in BAL fluid antioxidant potential. (2) Early increases in MIP-2, but not PGE2, are involved in the enhanced lung response to ozone in a hyperthyroid state. (3) Inflammatory mediator production (i.e., PGE2, MIP-2, MCP-1, and TNF-alpha) by alveolar macrophages plays a minimal role in the initial responses to ozone in a hyperthyroid state.
Keywords
Laboratory-animals; Animal-studies; Animals; Lung-disorders; Exposure-levels; Exposure-assessment; Antioxidation; Inhalation-studies; Pulmonary-system-disorders; Respiratory-system-disorders
CODEN
JTEHD6
Publication Date
20060301
Document Type
Journal Article
Email Address
ljh3@cdc.gov
Fiscal Year
2006
NTIS Accession No.
NTIS Price
Issue of Publication
6
ISSN
1528-7394
NIOSH Division
HELD
Source Name
Journal of Toxicology and Environmental Health, Part A: Current Issues
State
WV
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