High lung PDE5: a strong basis for treating pulmonary hypertension with PDE5 inhibitors

Biochem Biophys Res Commun. 2005 Sep 2;334(3):930-8. doi: 10.1016/j.bbrc.2005.06.183.


[3H]Vardenafil (Levitra) or [3H]tadalafil (Cialis) binding was used to quantify PDE5 in rat lung and heart tissue. Each radioligand bound to purified recombinant phosphodiesterase-5 (PDE5) or to PDE5 in crude extracts with strong affinity, high specificity, slow dissociation, and good stoichiometry. PDE5, the only 3H inhibitor-binding protein detected in extracts, was 15 times higher in lung than in heart extracts, and the level measured by PDE5 catalytic activity agreed with that determined by 3H inhibitor binding. High level of PDE5 in lung approximated that in penile corpus cavernosum, the tissue targeted by PDE5 inhibitors. PDE5 was the predominant cGMP-PDE in lung, and on a molar basis was five times higher than cGMP-dependent protein kinase (PKG), which phosphorylates PDE5 in vivo. The PDE5 level was one-half that of PKG in heart. Thus, abundance of PDE5 in lung vascular smooth muscle provides a strong molecular basis for PDE5 inhibitor treatment of pulmonary hypertension.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3',5'-Cyclic-GMP Phosphodiesterases / antagonists & inhibitors*
  • 3',5'-Cyclic-GMP Phosphodiesterases / metabolism*
  • Animals
  • Carbolines / metabolism
  • Chromatography, Gel
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Cyclic GMP-Dependent Protein Kinases / metabolism
  • Cyclic Nucleotide Phosphodiesterases, Type 5
  • Enzyme Inhibitors / therapeutic use*
  • Humans
  • Hypertension, Pulmonary / drug therapy*
  • Imidazoles / metabolism
  • Lung / enzymology*
  • Myocardium / enzymology
  • Piperazines / metabolism
  • Rats
  • Sulfones / metabolism
  • Tadalafil
  • Triazines / metabolism
  • Tritium
  • Vardenafil Dihydrochloride


  • Carbolines
  • Enzyme Inhibitors
  • Imidazoles
  • Piperazines
  • Sulfones
  • Triazines
  • Tritium
  • Vardenafil Dihydrochloride
  • Tadalafil
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic GMP-Dependent Protein Kinases
  • 3',5'-Cyclic-GMP Phosphodiesterases
  • Cyclic Nucleotide Phosphodiesterases, Type 5
  • PDE5A protein, human
  • Pde5a protein, rat