Hamster Trachea by Naturally Occurring and Synthetic Fibers Induction of Squamous Metaplasia in Organ Cultures of Updated Version

Asbestos exhibits many properties of classical tumor pro moters. These characteristics include the ability to stimulate proliferation and inhibit normal differentiation of cells. In organ cultures of trachea, crocidolite and amosite asbestos stimulate squamous metaplasia, a pathological process in which a rapidly proliferating squamous epithelium replaces the normal epithe lium. We hypothesized that the induction of metaplasia depends upon the fibrous nature of asbestos. Accordingly, several natu rally occurring and synthetic fibrous materials and their nonfibrous analogues were assessed for their ability to induce metaplastic changes in trachéalmucosa of the Syrian hamster. Ex posure to both crocidolite asbestos and fiberglass resulted in significant increases (p < 0.05) in squamous metaplasia over a range of dosages (1.0, 4.0, 16.0 mg/ml). Attapulgite (palygorskite) and both "long-" and "short-" fiber preparations of chrysotile asbestos had similar but less marked effects. Nonfibrous analogues of each material (riebeckite, antigorite, and glass particles) failed to produce metaplasia. Asbestos, and fibrous materials in general, appear to stimulate squamous metaplasia because of their fibrous geometry.