CFTR and cystic fibrosis: The intensity of the CFTR fluorescence signal was indeed unchanged in CFBE41o− and in 16HBE14o– cells co-treated with vardenafil and the inhibitors of PK A or G. The P-value for the comparison between CF vardenafil (Fig. 3B7) and CF vardenafil together with PKGi (Fig. 3B9) is 0.699 and that for the comparison between CF vardenafil (Fig. 3B7) and CF vardenafil together with PKAi (Fig. 3B10) is 0.818.