Effect of TGF-β superfamily members on BMP type I and type II receptor transcript levels. NHLF were stimulated with 5 ng/ml TGF-β1 or 100 ng/ml BMP-4 or BMP-7 for 24 h. Cells were harvested, RNA extracted and reverse transcribed, and a real-time quantitative PCR for ALK-2 (A), ALK-3 (B), ALK-6 (C), and BMPRII (D) was performed. Results are expressed as the ratio of each transcript relative to the geometric mean of mRNA expression of the housekeeping genes UBC, SDHA, and RPL13a. Data are mean ± SD of five independent experiments. *, p < 0.05, as compared to unstimulated cells.