Pulmonary alveolar epithelial cells, comprised of alveolar type I and type II epithelial cells, line more than 99% of the internal surface area of the lung. Type I cells are large squamous cells whose thin cytoplasmic extensions cover >95% of the internal lung surface. They contain aquaporins and exhibit the highest osmotic water permeability of any mammalian cell type. Type II cells, which cover 2-5% of the internal lung surface, produce, secrete, and recycle pulmonary surfactant. The currently accepted hypothesis is that Type II cells maintain pulmonary fluid homeostasis by regulating active Na+ transport in the lungs, whereas Type I cells are "inert" cells that provide only a barrier function. A recent study, however, suggests that Type I cells may also regulate ion and fluid transport. RPAEpiC from ScienCell Research Laboratories are isolated from rat lung. RPAEpiC are cryopreserved at P0 and delivered frozen. Each vial contains >1 x 106 cells in 1 ml volume. RPAEpiC are characterized by immunofluorescence with antibodies specific to cytokeratin-18. RPAEpiC are negative for, mycoplasma, bacteria, yeast, and fungi. RPAEpiC are guaranteed to further culture under the conditions provided by ScienCell Research Laboratories. This cell type, however, is not recommended for expanding or long term cultures since the cells would differentiate to type I alveolar epithelial cells immediately after plating and type I alveolar epithelial cells do not proliferate in culture. Recommended Medium It is recommended to use Alveolar Epithelial Cell Medium (AEpiCM, Cat. #3201) for culturing RPAEpiC in vitro.