Effect of chrysotile and crocidolite on the morphology and growth of rat pleural mesothelial cells.

The effects of the UICC asbestos fibers chrysotile A and crocidolite on the morphology and growth of rat pleural mesothelial cells were examined. The response was different according to the fiber used. Within 4 hr of treatment with 5, 10, 20, or 50 micrograms/ml of chrysotile fibers, cell morphology showed intense vacuolization, in both logarithmic and confluent cells. Following treatment of growing cells with 20 or 50 micrograms/ml of chrysotile fibers, cell spreading was also observed. Four hours after treatment of cells with 5, 10, or 20 micrograms/ml of crocidolite fibers, no such changes were seen. Vacuolization appeared later and was much less marked than for chrysotile fibers. The mesothelial cell population-doubling time of about 30 hr was not significantly altered by addition of 5 to 20 micrograms/ml of crocidolite fibers, but a concentration of 50 micrograms/ml lengthened doubling time to about 90 hr. Treatment with 5 or 10 micrograms/ml chrysotile fibers usually prolonged this time, but 20 or 50 micrograms/ml caused cell lysis. After 48 hr of incubation with both types of fiber, the proportion of mitosis was the same as in control cultures, whatever the fiber concentration, and asbestos fibers were often seen inside dividing cells.