The submerged condition decreases, and the A/L interface condition maintains, the expression of surfactant proteins. (A) Rat ATII cells were adhered for 1 day and cultured for 2, 4, or 6 days in 5% RS and 10 ng/ml KGF. Cells were harvested on Day 3, 5, or 7, and levels of surfactant proteins were analyzed by immunoblotting. Each condition is represented by two lanes from duplicate wells. This blot is representative of five independent experiments. (B) Levels of surfactant proteins from the immunoblotting data were normalized to β-actin and analyzed according to NIH Image (Bethesda, MD) (n = 5). (C) The mRNA concentrations of surfactant proteins were measured by real-time PCR from five independent experiments. These levels were normalized to the constitutive probe cyclophilin B (CyB). Values represent means ± SEMs of five independent experiments. A/L, air–liquid interface condition; Sub, submerged condition. *P < 0.05.