FIG. 3.

TGF-β1 inhibits gap junctional communication between alveolar epithelial cells. Primary rat type II cells were isolated and cultured for 6 days in minimal essential medium to produce a model type I cell monolayer. The cells were then treated with varying amounts of TGF-β1 for 16 h; then the extent of gap junctional communication was determined by visualizing the intercellular transfer of calcein microinjected into individual cells with fluorescence microscopy. Dye transfer was quantified by counting the number of calcein-labeled cells per microinjection. Data were combined from two independent experiments counting ≥20 microinjections/treatment. Increasing concentrations of TGF-β1 significantly decreased intercellular communication, as determined by t test (*p < 0.05).