Time course of markers of alveolar epithelium differentiation from AT2 to AT1 cells. Prosurfactant protein-C (pro-SP-C; marker for AT2 cells), is highly expressed at days 0 and 1, but shows a distinct reduction beginning on day 2, although slightly less with heparin. At days 3 and 4, heparin treatment accelerates the increasing reduction of pro-SP-C. No pro-SP-C expression is evident at days 7 and 9. Plasminogen activator inhibitor-1 (PAI-1; marker for AT1 cells), was faintly detectable at day 1 and steadily increased as the time course progressed to day 9. Another marker for AT1 cells is aquaporin5 (Aqp5), which is detectable at day 7, but was very evident by day 9. GAPDH of the same blots is shown for normalization. Blots shown are representative of the similar results of three separate experiments.