Ingestion, cytotoxicity, and early morphological effects of asbestos on Tetrahymena

Crocidolite asbestos fibers are rapidly ingested in large amounts by Tetrahymena. This varies little with incubation time of fibers in the culture medium or with dilution of the medium. The ingested fibers form large, oblong bundles in the cell rather than the normal spherical food vacuoles. In addition, crocidolite results in a rapid dose dependent induction of various minor morphological abnormalities. At 0.1-3 mg/ml these are observed in approximately one third of the population. Crocidolite is, however, not cytotoxic to Tetrahymena even in these high concentrations as measured by cell death and population doubling time. Phagocytosis and cytotoxicity are thus not related in this cell. Preliminary studies indicate that all the U.I.C.C. standard reference asbestos samples have largely similar effects but that their ability to induce abnormalities depends on the species of Tetrahymena used. For studies of the effects of asbestos Tetrahymena should be a suitable model system because the massive ingestion of fibers and its short generation time should facilitate rapid detection of adverse effects. Among such effects is the induction of heterogenous cell lines. This may involve modification of non-nucleic acid carried hereditary (cytotactic) information.