Effect of erionite on the pleural mesothelium of the Fischer 344 rat.
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).


METHODS
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 microns, 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.
Fraire
A E
AE
University of Massachusetts Medical Center, Worcester 01655, USA.
Greenberg
S D
SD
Spjut
H J
HJ
Dodson
R F
RF
Williams
G
G
Lach-Pasko
E
E
Roggli
V L
VL
D000818:Animals; D002273:Carcinogens / Q000494:pharmacology; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004848:Epithelium / Q000187:drug effects; D005260:Female; D005355:Fibrosis; D005500:Follow-Up Studies; D005549:Foreign-Body Reaction / Q000139:chemically induced; D006965:Hyperplasia; D008168:Lung / Q000187:drug effects; D008171:Lung Diseases / Q000139:chemically induced; D008654:Mesothelioma / Q000139:chemically induced; D008853:Microscopy; D009505:Nevada; D009922:Oregon; D010994:Pleura / Q000187:drug effects*; D010995:Pleural Diseases / Q000139:chemically induced; D010997:Pleural Neoplasms / Q000139:chemically induced; D010998:Pleurisy / Q000139:chemically induced; D011014:Pneumonia / Q000139:chemically induced; D011658:Pulmonary Fibrosis / Q000139:chemically induced; D051381:Rats; D011916:Rats, Inbred F344; D017641:Zeolites / Q000737:chemistry / Q000494:pharmacology*
D002273:Carcinogens; C083174:erionite; D017641:Zeolites