© 1996 Oxford University Press
research-article |
Pulmonary and Pleural Responses in Fischer 344 Rats Following Short-Term Inhalation of a Synthetic Vitreous Fiber
II. Pathobiologic Responses
Chemical Industry Institute of Toxicology P.O. Box 12137, Research Triangle Park, North Carolina 27709
Received March 14, 1995; accepted September 27, 1995
The pleura is a target site for toxic effects induced by a variety of fibrous particulates, including both natural mineral and man made vitreous fibers. We examined selected cytological and bio chemical indicators of inflammation in both the pleural compart ment and pulmonary parenchyma in F344 rats following inhala tion of RCF-1, a kaolin-based ceramic fiber. Male F344 rats were exposed by Inhalation to 89 mg/m3 (2645 WHO fibers/cc) RCF-1 6 hr/day for 5 consecutive days. In lung parenchyma, cytological and biochemical inflammatory responses occurred rapidly following exposure. In contrast, pleural responses were delayed in onset and of a much smaller magnitude than those observed in lung. At both Day 1 and Day 28 postexposure, increased quantities of lactate dehydrogenase, N-acetyl glucosaminidase, alkaline phosphatase, albumin, and neutrophils were present in bronchoalveolar lavage fluid. These responses were attenuated at the latter time point. No significant responses were detected in pleural lavage fluid until 28 days following exposure, at which time elevated numbers of macrophages and eosinophils, but not neutrophils, were observed. Increased albumin and fibronectin were also ob served in PLF at this latter time point. These findings demonstrate that the onset of pleural and pulmonary responses following inhalation of RCF-1 are temporally separated and that pleural injury may increase in severity with time following exposure. The increase in severity of pleural inflammation found in the postexposure period cannot be readily explained by fiber translocation.