Saw palmetto extract enhances erectile responses by inhibition of phosphodiesterase 5 activity and increase in inducible nitric oxide synthase messenger ribonucleic acid expression in rat and rabbit corpus cavernosum

Urology. 2013 Jun;81(6):1380.e7-13. doi: 10.1016/j.urology.2012.12.062. Epub 2013 Apr 23.


Objective: To evaluate whether saw palmetto extract (SPE) relaxes corpus cavernosum and explore the underlying mechanisms.

Methods: Forty Sprague-Dawley rats and 30 New Zealand rabbits were randomly allocated into 3 SPE-treated groups (low-, middle-, and high-dose) and 1 saline-treated control group. SPE was administered intragastrically for 7 consecutive days. Another 23 rats treated with sildenafil were used to appraise the erectile response to electrical stimulation of nerves in the corpus cavernosum. The erectile functions of rats and rabbits were evaluated 24 hours after the last SPE administration or 15 minutes after intragastric sildenafil. Outcome measures included corpus cavernosum electrical activity recording, phosphodiesterase 5 (PDE5) activity detected by the colorimetric quantitative method, and messenger ribonucleic acid (mRNA) expression level for PDE5 and inducible nitric oxide synthase (iNOS) determined using real-time polymerase chain reaction.

Results: In the SPE-treated animals, the relaxant response to electrical stimulation of nerves in the corpus cavernosum, reflected by the amplitude of the electrical activity within the cavernosum, was significantly and dose-dependently augmented. Similar effects were observed in the sildenafil-treated rats. PDE5 activity in rat and rabbit corpus cavernosum tissues was significantly and dose-dependently inhibited in SPE-treated animals, whereas the iNOS mRNA level increased compared with the saline group. PDE5 mRNA, however, was only significantly enhanced in the rats treated with the middle dose of SPE.

Conclusion: The results suggest that SPE may have potential application value for the prevention or treatment of erectile dysfunction through an increase in iNOS mRNA expression and inhibition of PDE5 activity in corpus cavernosum smooth muscles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Analysis of Variance
  • Animals
  • Cyclic Nucleotide Phosphodiesterases, Type 5 / genetics
  • Cyclic Nucleotide Phosphodiesterases, Type 5 / metabolism*
  • Electric Stimulation
  • Enzyme Activation / drug effects*
  • Male
  • Nitric Oxide Synthase Type II / genetics
  • Penile Erection / drug effects*
  • Penis / drug effects
  • Penis / metabolism*
  • Penis / physiology
  • Phosphodiesterase 5 Inhibitors / pharmacology*
  • Piperazines / pharmacology
  • Plant Extracts / pharmacology*
  • Purines / pharmacology
  • RNA, Messenger / metabolism*
  • Rabbits
  • Random Allocation
  • Rats
  • Rats, Sprague-Dawley
  • Serenoa
  • Sildenafil Citrate
  • Sulfones / pharmacology


  • Phosphodiesterase 5 Inhibitors
  • Piperazines
  • Plant Extracts
  • Purines
  • RNA, Messenger
  • Sulfones
  • Sildenafil Citrate
  • Nitric Oxide Synthase Type II
  • Cyclic Nucleotide Phosphodiesterases, Type 5
  • saw palmetto extract