Characterization of a lung epithelial cell strain with potential applications in toxicological studies.

An epithelial cell strain (LEC, lung epithelial cells) was established from the lungs of an adult Fischer-344 rat. The cells had properties of normal, untransformed cells in culture which include contact inhibition of growth, inability to grow in soft agar, and inability to form tumors when injected subcutaneously into syngeneic hosts. Low passage LEC were diploid, while high passage cells were aneuploid with an extra chromosome. LEC resembled type II alveolar cell in vivo in that they had lamellar inclusions in their cytoplasm, microvilli on cell surface, and that they could incorporate [14C] choline into disaturated phosphatidyl choline, a surfactant lipid. The ability of LEC to activate procarcinogens was demonstrated by co-cultivation of LEC with Chinese hamster ovary (CHO) cells in the presence of procarcinogens benzo[a]pyrene and 3-methyl cholanthrene. While these procarcinogens were non-mutagenic to CHO cells which lacked the metabolic activation capacity, they were mutagenic when LEC were co-cultured with the CHO cells. By maintaining LEC cells on collagen gel without overlying medium, the cells could be directly exposed to noxious airborne agents. Using this technique, the cytotoxicity of NO2 was detected. Because of the lung epithelial origin, the ability to metabolize xenobiotics, and the exposure system to airborne agents, the LEC strain can be a useful and relevant in vitro system for the toxicological studies of inhalable materials.