title: 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.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai, China. sryang@shmu.edu.cn
authors.forename: Surong
authors.initials: S
authors.lastname: Yang
authors.forename: Changrui
authors.initials: C
authors.lastname: Chen
authors.forename: Yiying
authors.initials: Y
authors.lastname: Li
authors.forename: Zhenghua
authors.initials: Z
authors.lastname: Ren
authors.forename: Yungang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Gantong
authors.initials: G
authors.lastname: Wu
authors.forename: Hao
authors.initials: H
authors.lastname: Wang
authors.forename: Zhenzhen
authors.initials: Z
authors.lastname: Hu
authors.forename: Minghui
authors.initials: M
authors.lastname: Yao
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5 / Q000235:genetics / Q000378:metabolism*; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects*; D008297:Male; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D010410:Penile Erection / Q000187:drug effects*; D010413:Penis / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D010936:Plant Extracts / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D011817:Rabbits; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D028024:Serenoa; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology
chemical_list: D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D010936:Plant Extracts; D011687:Purines; D012333:RNA, Messenger; D013450:Sulfones; D000068677:Sildenafil Citrate; D052247:Nitric Oxide Synthase Type II; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C040972:saw palmetto extract