Chest
Volume 111, Issue 5, May 1997, Pages 1375-1380
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Laboratory and Animal Investigations
Effect of Erionite on the Pleural Mesothelium of the Fischer 344 Rat

https://doi.org/10.1378/chest.111.5.1375Get rights and content

Objective

This study sought to assess the fibrogenic and carcinogenic potential of erionite (a fibrous zeolite) on the pleural mesothelium of the Fischer 344 rat (n=24).

Design

The study was designed to examine rat pleural mesothelial changes by three independent observers at timed intervals, ranging from 1 to 480 days postinoculation using erionite from the Pine Valley, Nevada (USA) area. The mean length and width of the erionite fibers were 2.29 and 0.48 μm, respectively. Only microscopic observations made by majority (2/3) or unanimity (3/3) were accepted for final diagnosis.

Results

Pleural and lung tissue were available for examination in 21 of the 24 rats. Fibrosis, chronic inflammation, and foreign body reaction occurred in 6 of 21 rats. Mesothelial hyperplasia and dysplasia occurred in 9 and 3 of the 21 rats, respectively. A single mesothelioma was identified at 434 days in a rat that had gross nodular pleural lesions.

Conclusions

The findings reported herein confirm the strong fibrogenic potential of erionite but are at variance with previous studies reporting much higher yields of mesothelioma. The reasons for the low yield of mesothelioma in this study are not known, but may be related to the study design, the strict criteria used for histopathologic diagnosis, and/or possible differences in erionite physicochemical properties, associated with its geographic distribution, most previous animal studies having used erionite from the Rome, Oregon (USA) area.

Section snippets

Fiber Evaluation

The erionite fibers were characterized by suspending random samples in distilled water and collecting them on a 0.2-μm polycarbonate filter. Next, the filter surface and its adherent erionite fibers were coated with evaporated carbon, and extraction replicas were made by dissolving the filter matrix in chloroform. The replicas were analyzed at a magnification of ×9,400 using an image analysis system (EDAX NX-2; EDAX Intl;

Mahwah, NJ) interfaced to an electron microscope (JEOL 100 CX, JEOL Ltd;

RESULTS

Pleural fibrosis, often accompanied by adhesive bands to the chest wall, was prominent and was found in 9 of 21 cases (Fig 3). Foreign body granuloma were found in 6 of the 21 cases and often included multinucleated giant cells. The single mesothelioma developing in this series had a gross multinodular appearance and extended to the diaphragmatic surface. This fibrosarcomatous mesothelioma was invasive and extended down from the pleura into the underlying lung tissue (Fig 4). Although diagnosed

DISCUSSION

Erionite, a fibrous zeolite (hydrated aluminum silicate), has a strong carcinogenic potential in humans.

Artvinli and Baris5 determined the prevalence of pleural mesothelioma in the Turkish Anatolian village of Tuzkoy, well known for its erionite-rich soil. Kizilkoy, a village 12 km away, was used as control village. Sixty-seven deaths were recorded in Tuzkoy over a period of 3 years, and of these, 41 were attributed to malignancies. Fifteen of these 41 malignancies were mesotheliomas. There

ACKNOWLEDGMENT

The authors are grateful to Karen Ginese for her assistance with the preparation of the manuscript.

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Funded by Baylor Grant BRSG 520-G16261 and by the Baylor Pulmonary Pathology Research Grant, Baylor College of Medicine, Houston.

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