title: Visualization and tissue distribution of alpha1L-adrenoceptor in human prostate by the fluorescently labeled ligand Alexa-488-silodosin.
abstract: OBJECTIVE
  Although alpha(1L)-adrenoceptor is recognized as a target of alpha(1) antagonist therapy for benign prostatic hyperplasia, the most common techniques, such as immunohistochemistry and in situ hybridization, are not applicable to examine alpha(1L)-AR vs alpha(1A)-AR tissue distribution because alpha(1L)-AR is now considered another phenotype sharing the alpha(1A)-AR gene and protein molecule. We labeled the alpha(1A) and alpha(1L)-adrenoceptor selective antagonist silodosin (Kissei Pharmaceutical, Matsumoto, Japan) with the fluorophore Alexa Fluor(R) 488 (Alexa-488-silodosin) to visualize alpha(1L)-AR expression.
  
  
  METHODS
  Radioligand binding and functional bioassay experiments were done to assess alpha(1)-AR expression in Chinese hamster ovary cells and human prostate tissues. Confocal imaging was subsequently performed.
  
  
  RESULTS
  Although Alexa-488-silodosin had about 10 times lower affinity for all alpha(1)-AR subtypes than silodosin in binding and functional studies, it had high selectivity to alpha(1A) and alpha(1L)-ARs. Confocal imaging revealed clear localization of fluorescence on the membrane of Chinese hamster ovary cells expressing alpha(1A)-AR but not alpha(1B)-and alpha(1D)-ARs, and in the muscle layer of the human prostate. The fluorescent signal in Chinese hamster ovary cells disappeared in the presence of 3 nM prazosin but fluorescence was observed in the human prostate even in the presence of 100 nM prazosin.
  
  
  CONCLUSIONS
  Alexa-488-silodosin is a powerful fluorescent probe with high selectivity to alpha(1A) and alpha(1L)-ARs. Thus, Alexa-488-silodosin successfully visualizes the site of alpha(1L)-ARs in the muscle layer of the human prostate without losing its distinct pharmacological profile.
authors.affiliation: Division of Pharmacology, Department of Biochemistry and Bioinformative Sciences, University of Fukui, Eiheiji, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Morishima
authors.forename: Fumiko
authors.initials: F
authors.lastname: Suzuki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nishimune
authors.forename: Hatsumi
authors.initials: H
authors.lastname: Yoshiki
authors.forename: Hironobu
authors.initials: H
authors.lastname: Akino
authors.forename: Osamu
authors.initials: O
authors.lastname: Yokoyama
authors.forename: Ikunobu
authors.initials: I
authors.lastname: Muramatsu
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005453:Fluorescence; D005464:Fluorobenzenes; D007211:Indoles; D008297:Male; D011467:Prostate / Q000737:chemistry* / Q000378:metabolism*; D018340:Receptors, Adrenergic, alpha-1 / Q000032:analysis* / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C513915:AlexaFluor 488 carboxylic acid tetrafluorophenyl ester; D005464:Fluorobenzenes; D007211:Indoles; D018340:Receptors, Adrenergic, alpha-1; C095285:silodosin