Enhanced release of a chemoattractant for alveolar macrophages after asbestos inhalation

Alveolar macrophage supernatants from 2 groups of asbestos-exposed rats and a group of sham-exposed rats were tested for chemoattractant activity towards rat alveolar macrophages. Enhanced chemotaxin release was observed in culture supernatants from both crocidolite and chrysotile asbestos-exposed rats when compared with supernatants from sham-exposed rats. These between-group differences persisted for as long as 15 months after exposure had ceased. Chemotactic factor release was maximal after 24 h of culture in all animal groups. Partial characterization of the chemoattractant from each of the 3 rat groups revealed that it was thermolabile, nondialyzable, and trypsin-sensitive. Separation on SDS-polyacrylamide gel electrophoresis revealed 3 major peaks of activity. The production of the chemotaxin in supernatants from asbestos-exposed rats was partially inhibited by both actinomycin D and puromycin. These agents had no appreciable effect on the production of chemoattractant in cultures from sham-exposed animals. The enhanced release of an alveolar macrophage chemoattractant after asbestos inhalation may explain why macrophages accumulate at sites of asbestos deposition in the lungs.