SECRETION OF ALPHA-1-ANTITRYPSIN BY ALVEOLAR EPITHELIAL-CELLS

We have investigated the ability of alveolar epithelial cells (human A 549 cell line and rat type-II pneumocytes) to produce al-antitrypsin ( AAT). Northern blot analysis demonstrated the presence of an AAT-speci fic mRNA transcript in A549 cells. Unstimulated A549 cells secreted im munoreactive AAT at a rate of 0.51 +/- 0.04 ng/10(6) cells/h, with a m odified glycosylation compared to serum AAT. AAT formed a complex with neutrophil elastase. Rat type-II pneumocytes secreted immunoreactive AAT. Our results suggest that alveolar epithelial cells could particip ate in antiprotease defense within the lung through local AAT producti on.