Minerals Modulated by Serum and by Transforming Growth Sensitivity of Hamster Tracheal Epithelial Cells to Asbestiform

A number of proliferativiand cytotoxic responses similar to those induced by classical tumor promoters such as 12-0-tetradecanoylphorbol13-acetate occur in trachea! epithelial cells and organ cultures exposed to asbestiform minerals. In these studies, cloned diploid hamster trachea! epithelial cells were examined in a number of short term (3-24 h) and long term (>24 h) biological assays for their responsiveness to crocidolite asbestos in comparison to other fibers (chrysotile asbestos, Code 100 fiberglass) and particulates (riebeckite, antigorite, glass beads). In addi tion, the influence of serum on the biological effects of crocidolite were assessed. In 10% serum-containing medium, low concentrations of cro cidolite (1.0 fig/cm2 dish) stimulated cellular proliferation (measured as increased |'H]thymidine incorporation), and concentrations >5 ¿ig/cm2 dish were cytotoxic (measured by decreased colony forming efficiency). In 2% serum-containing medium, lower concentrations of fibers (0.1-0.5 nnA'iir dish) caused increases in | 'I I|i In iniilmr incorporation and colony forming efficiency whereas higher concentrations of fibers were required for responses equitoxic to those observed in 10% serum. Crocidoliteinduced |'H]thj nudine incorporation was inhibited when 2% serumcontaining medium was supplemented with transforming growth factor type 0 at concentrations (3 ng/ml) which give rise to altered morphology of hamster trachea! epithelial cells. Furthermore, the profiles of colony forming efficiency and "Cr release of cells grown in the presence of transforming growth factor ßresembled those of cells grown in 10% serum. Results suggest that the phenotypic changes induced by serum factors such as transforming growth factor ft influence the sensitivity of hamster trachea! epithelial cells to crocidolite asbestos.