Phosphodiesterase type 5 is not upregulated by tadalafil in cultures of human penile cells.
Vernet D, Magee T, Qian A, Nolazco G, Rajfer J, Gonzalez-Cadavid N. Phosphodiesterase type 5 is not upregulated by tadalafil in cultures of human penile cells. J Sex Med. 2006 Jan; 3(1):84-94; discussion 94-5.