ASBESTOS EXPOSURE ENHANCES THE RELEASE OF FIBROBLAST GROWTH-FACTOR BY SHEEP ALVEOLAR MACROPHAGES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 33  (4) , 275-285
Abstract
Interaction between free airway cells (FAC) and lung fibroblasts was studied in a sheep model of asbestosis. Three groups of 6 sheep each received, respectively, by repeated intratracheal instillations, saline (control), 328 mg (low dose) and 2282 mg (high dose) of chrysotile B asbestos. Sixteen months after the 1st instillation, FAC obtained by segmental bronchoalveolar lavage (BAL) of sheep in each group were incubated for various intervals, and the effect of their culture supernatants (FAC-N) on human embryonic lung fibroblast proliferation was determined. FAC-SN from control animals stimulated thymidine (3H-TdR) incorporation by lung fibroblasts 2- to 3-fold compared to untreated cultures. Maximal stimulation was observed at 48 h and was correlated with a significant increase of the fibroblast population at 72 h. FAC population form control sheep consisted primarily of macrophages (79%) and lymphocytes (15%), and separation of these 2 cell populations indicated that only macrophages produced the fibroblast-stimulating activity. Production occurred within 1 h of incubation and was maximal between 2 and 4 h. This activity was nondialyzable and stable at 56.degree. C for 30 min, but was destroyed at 80.degree. C and low pH. FAC-SN from sheep exposed to asbestos stimulated 3H-TdR incorporation by fibroblasts 5- to 6-fold compared to 2- to 3-fold for control FAC-SN. This activity may have modulated fibrogenesis and been involved in the eventual fibrogenic response to asbestos.