Pulmonary peptides and autacoids in experimentally induced asbestosis in rats
Previous studies have clearly established the presence of various peptides and autacoids in the lung, being mostly localized in neuroendocrine cells and mast cells. Proliferation of these cell types following asbestos fiber inhalation bas been described. In order to better understand the biochemical basis of asbestosis, this study investigated the lung levels of serotonin, histamine and various peptides following asbestos exposure. Asbestosis was induced in male Wistar rats by a single intratracheal injection of 5 or 10 mg of standard UICC Canadian Chrysotile B, while control animals received only the saline carrier. After various exposure times, lung extracts were prepared and measured for content in autacoids and peptides. Isolated rat lung cells were also prepared from normal and asbestos exposed rats and then were fractionated on BSA gradients and measured for their content in autacoids and peptides. The following changes were observed, serotonin and histamine contents increased in a parallel manner in tissue extracts beginning at times of one month following asbestos exposure. VIP content in tissue extracts increased after 3 months while bombesin content increased only after 6 months asbestos exposure. With isolated and fractionated rat lung cells, the changes in serotonin, histamine and VIP content occurred in subpopulations enriched in mast cells. The occurence of neuroendocrine cells in these specific cell subpopulations remains to be clearly established.