F2RL1 and cystic fibrosis: When the trachea were exposed to PAR2-AP (100 μM), large amounts of secretion were observed in tracheas from both WT (0.10±0.01 nl/min, 22 glands, four mice) and CF mice (0.15±0.01 nl/min, 15 glands, three mice), with no significant difference between the two groups but there is no secretion from PAR-2 knock out mice (Figure 6A and B).