Comparison of phagocytosis of uncoated versus coated asbestos fibers by cultured human pulmonary alveolar macrophages.

THE ENVIRONMENT AND THE LUNG 39$ achieved by prior culture for five days in DMEM + 0.5% FCS) and fibroblast cell counts determined after one, two, and four days. DMEM + 0.5% FCS ± asbestos incubated for four hours as controls. Supernatants from unexposed PAM had no influence on fibroblast replication rate. In contrast, supernatants from PAM exposed to asbestos significantly increased the rate of fibroblasts doubling; the doubling time decreasing five-fold from a control of 310±21 hours to 54±4 hours, P<.001. The stimulation of fibroblast replication was readily apparent by 48 hours with 68±2 X 10 cells per plate in the group treated with asbestos exposed PAM supematants compared to only 43±3 X 108 cells per plate in the control groups. This study demonstrates that asbestos-treated PAM release factor(s) promoting human lung fibroblast replication, and suggests a possible role for PAM in the formation of the fibroblast clusters observed in the early lesions of asbestosis.