CHARACTERIZATION OF THE A549 CELL-LINE AS A TYPE-II PULMONARY EPITHELIAL-CELL MODEL FOR DRUG-METABOLISM

Multiple cell types contribute to the pulmonary barrier including Type I and Type II alveolar epithelium. The objective of this research was to establish and characterize an in vitro model of Type II alveolar e pithelium using the A549 human lung adenocarcinoma cell line. A549 cel ls form confluent monolayers with Type II characteristic morphology an d tannic acid staining for typical lamellar bodies. A549 cells possess P450 IA1 and P450 IIB6 as determined by Western blots. Both CYPIA1 an d CYPIIB6 P450 isozymes were determined to be functional with the fluo rescent resorufin assay. Only the IA1 isozyme was observed to be induc ible with selected polycyclic hydrocarbons. Uptake and transport exper iments were carried out in cluster plates and in Snapwells. Cationized ferritin, a nonspecific absorbtive marker, was found to be taken up b y the cells in a concentration-, time-, and temperature-dependent fash ion. Lucifer yellow, a fluid-phase marker, was not internalized by the A549 cells. Transferrin, a representative receptor-mediated endocytic marker, was found to be taken up by the cells in a concentration-depe ndent and competitive fashion. Transport experiments involving fluores cein-transferrin also showed that A549 monolayers were polarized, with a greater amount of intracellular transferrin being transported out o f the basolateral side of the cells. The experimental data agree favor ably with literature for primary cultures of Type II pulmonary epithel ial cells. These results indicated that the A549 cell line may be usef ul for the studying the metabolic and macromolecule processing contrib utions of alveolar Type II cells to mechanisms of drug delivery at the pulmonary epithelium. (C) 1998 Academic Press.