Environmental Health Perspectives 105, Supplement 5, September 1997: Article by

Environmental Health Perspectives 105, Supplement 5, September 1997

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Comparison of Pleural Responses of Rats and Hamsters to Subchronic Inhalation of Refractory Ceramic Fibers

Jeffrey I. Everitt, Thomas R. Gelzleichter, Edilberto Bermudez, James B. Mangum, Brian A. Wong, Derek B. Janszen, and Owen R. Moss

Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina

Abstract
In the present subchronic study, we compared pleural inflammation, visceral pleural collagen deposition, and visceral and parietal pleural mesothelial cell proliferation in rats and hamsters identically exposed to a kaolin-based refractory ceramic fiber, (RCF)-1 by nose-only inhalation exposure, and correlated the results to translocation of fibers to the pleural cavity. Fischer 344 rats and Syrian golden hamsters were exposed to 650 fibers/cc of RCF-1, for 4 hr/day, 5 days/week for 12 weeks. Following 4 and 12 weeks of exposure, and after a 12-week recovery period, pleural lavage fluid was analyzed for cytologic and biochemical evidence of inflammation. Visceral and parietal pleural mesothelial cell proliferation was assessed by immunocytochemical detection of bromodeoxyuridine incorporation. Pleural collagen was quantitated using morphometric analysis of lung sections stained with Sirius Red. Fiber-exposed rats and hamsters had qualitatively similar pleural inflammation at each time point. Mesothelial cell proliferation was more pronounced in hamsters than in rats at each time point and at each site. In both species, the mesothelial cell labeling index was highest in the parietal pleural mesothelial cells lining the surface of the diaphragm at each time point. Hamsters but not rats had significantly elevated collagen in the visceral pleura at the 12-week postexposure time point. Fibers were found in the pleural cavities of both species at each time point. These fibers were generally short and thin. These results suggest that mesothelial cell proliferation and fibroproliferative changes in the pleura of rodents following short-term inhalation exposure are associated with fiber translocation to the pleura and may be predictive of chronic pleural disease outcomes following long-term exposure. -- Environ Health Perspect 105(Suppl 5):1209-1213 (1997)

Key words : fiber, inhalation, pleura, hamster, cell proliferation

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 26 March 1997; accepted 11 April 1997.
We acknowledge the helpful discussions of our colleagues P. Ferriola and F. Miller and the scientific editing assistance of B. Kuyper. This work was funded in part by grants from the North American Insulation Manufacturers Association and the Refractory Ceramic Fiber Coalition.
Address correspondence to: Dr. J.I. Everitt, Chemical Industry Institute of Toxicology, P.O. Box 12137, 6 Davis Drive, Research Triangle Park, NC 27709. Telephone: (919) 558-1267. Fax: (919) 558-1300. E-mail: everitt@ciit.org
Abbreviations used: BrdU, bromodeoxyuridine; HBSS, Hanks balanced salt solution; L/D, length/diameter; LDH, lactate dehydrogenase; NAG, N -acetylglucosaminidase; PLF, pleural lavage fluid; RCF, refractory ceramic fiber.

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Last Update: October 31, 1997