Fibrogenic potential of intratracheally instilled quartz, ferric oxide, fibrous glass, and hydrated alumina in hamsters.
Pulmonary fibrosis was induced in hamsters by different doses of intratracheally instilled quartz (60676860), quartz and ferric-oxide (1309371), fibrous-glass (14808607), and hydrated-alumina (21645512), as a first step in the development of an animal model for determining the role of fibrosis in the etiology and pathogenesis of lung cancer. Sixteen groups of 25 male Syrian- golden-hamsters, approximately 10 weeks of age, were exposed to 15 weekly instillations of one of four doses of one of the materials in saline. Two additional groups were maintained as saline and cage controls. Survival was significantly decreased in the groups with the two highest weekly doses of quartz (6.0 and 3.3 milligrams) or quartz and ferric-oxide (6.0 and 3.3 milligrams of each). Grading for severity of pulmonary fibrosis was complicated by the presence of chronic pulmonary congestion and edema associated with chronic heart disease, with accompanying fibrosis in both control and exposed animals. The incidence and severity of septal fibrosis correlated well with the dose of instilled quartz or quartz and ferric-oxide, but not as well with the dose of fibrous glass or alumina. However, no animal had large, discrete foci of dense fibrous tissue containing solid areas of mature collagen, as observed in classical silicosis of man; and the fibrosis was less severe than reported in the literature for rats exposed to quartz. Granulomatous inflammation was the most striking pulmonary lesion, with an incidence and severity that in most cases was related to dose. The authors conclude that the most appropriate material to induce pulmonary fibrosis in the hamster is quartz, but that the rat appears to be the preferred species in the development of an animal model to study particulate induced fibrosis and its relationship to pulmonary cancer.