title: Muscarinic and alpha 1-adrenergic receptor binding characteristics of saw palmetto extract in rat lower urinary tract.
abstract: OBJECTIVE
  To elucidate the in vitro and ex vivo effects of saw palmetto extract (SPE) on autonomic receptors in the rat lower urinary tract.
  
  
  METHODS
  The in vitro binding affinities for alpha 1-adrenergic, muscarinic, and purinergic receptors in the rat prostate and bladder were measured by radioligand binding assays. Rats received vehicle or SPE (0.6 to 60 mg/kg/day) orally for 4 weeks, and alpha 1-adrenergic and muscarinic receptor binding in tissues of these rats were measured.
  
  
  RESULTS
  Saw palmetto extract inhibited specific binding of [3H]prazosin and [N-methyl-3H]scopolamine methyl chloride (NMS) but not alpha, beta-methylene adenosine triphosphate [2,8-(3)H]tetrasodium salt in the rat prostate and bladder. The binding activity of SPE for muscarinic receptors was four times greater than that for alpha 1-adrenergic receptors. Scatchard analysis revealed that SPE significantly reduced the maximal number of binding sites (Bmax) for each radioligand in the prostate and bladder under in vitro condition. Repeated oral administration of SPE to rats brought about significant alteration in Bmax for prostatic [3H]prazosin binding and for bladder [3H]NMS binding. Such alteration by SPE was selective to the receptors in the lower urinary tract.
  
  
  CONCLUSIONS
  Saw palmetto extract exerts significant binding activity on autonomic receptors in the lower urinary tract under in vitro and in vivo conditions.
authors.affiliation: Department of Pharmacokinetics and Pharmacodynamics, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Suzuki
authors.forename: Tomomi
authors.initials: T
authors.lastname: Oki
authors.forename: Tomomi
authors.initials: T
authors.lastname: Sugiyama
authors.forename: Keizo
authors.initials: K
authors.lastname: Umegaki
authors.forename: Shinya
authors.initials: S
authors.lastname: Uchida
authors.forename: Shizuo
authors.initials: S
authors.lastname: Yamada
mesh_terms: D000726:Androgen Antagonists / Q000494:pharmacology; D000818:Animals; D066298:In Vitro Techniques; D008297:Male; D023421:Models, Animal; D010936:Plant Extracts / Q000494:pharmacology*; D011467:Prostate / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects*; D011976:Receptors, Muscarinic / Q000187:drug effects*; D011983:Receptors, Purinergic / Q000187:drug effects*; D028024:Serenoa; D001743:Urinary Bladder / Q000187:drug effects*
chemical_list: D000726:Androgen Antagonists; D010936:Plant Extracts; D018340:Receptors, Adrenergic, alpha-1; D011976:Receptors, Muscarinic; D011983:Receptors, Purinergic; C040972:saw palmetto extract