THE EFFECT OF FIBRONECTIN ON CYTOSKELETON STRUCTURE AND TRANSEPITHELIAL RESISTANCE OF ALVEOLAR TYPE-II CELLS IN PRIMARY CULTURE

The cytoskeleton of alveolar type II cells on different matrices has b een examined, and the bioelectric properties of these cells grown as m onolayers in primary culture has be measured using Ussing-type chamber s, to determine whether the extracellular matrix affects the cytoskele tal organization of alveolar type II cells and whether any such intera ctions influence their physiological functions. Alveolar type II cells cultured on a fibronectin substratum spread slowly over a 6-day perio d to produce cells of extremely large diameter. The cytoskeletal struc ture of these cells was characterized by a more marked accumulation of large bundles of actin and a finer network of keratin than cells grow n on a collagen substratum. The transepithelial resistances of monolay ers grown on a fibronectin substratum were much higher than those on a collagen substratum. These results indicate that alveolar type II cel ls cultured on fibronectin can form tighter, better organized and more polarized monolayers in primary culture, which suggests that fibronec tin may have a physiologically important role in the maintenance of th e alveolar wall.