title: Increased expression of endothelin B receptors in the diabetic rabbit urinary bladder: functional relevance.
abstract: OBJECTIVE
  To determine the effect of diabetes mellitus on the density and distribution of endothelin A (ETA ) and endothelin B (ETB ) receptor subtypes in the rabbit urinary bladder, and to assess the in vitro functional properties of endothelin-1 (ET-1) receptors in bladder smooth muscle strips from diabetic and healthy rabbits.
  
  
  METHODS
  Diabetes mellitus was induced in six male New Zealand White rabbits with alloxan and their urinary bladders excised 6 months after the induction of diabetes. On serial detrusor and bladder neck sections, low- and high-resolution autoradiography was performed using radioligands for ET-1, ETA and ETB receptors; these sections were then analysed densitometrically. The results were compared with those from six age-matched healthy control rabbits. Functional responses were investigated using isometric tension studies.
  
  
  RESULTS
  ETA and ETB receptor binding sites were localized to both the urothelium and smooth muscle of the detrusor and bladder neck. There were significantly more ETB receptor binding sites in the diabetic detrusor and bladder neck sections than in controls. ET-1 smooth muscle contractile responses were ETA receptor-mediated. The smooth muscle contractile responses to ET-1 were unaltered in the detrusor, but significantly impaired in the bladder neck of diabetic animals compared with controls.
  
  
  CONCLUSIONS
  Alteration in the expression of ETB receptors and in vitro contractile smooth muscle responses to ET-1 in the diabetic rabbit urinary bladder neck may play a role in the pathophysiology of diabetic cystopathy.
authors.affiliation: Department of Urology, Royal Free Hospital, London, UK.
authors.forename: F H
authors.initials: FH
authors.lastname: Mumtaz
authors.forename: M R
authors.initials: MR
authors.lastname: Dashwood
authors.forename: C S
authors.initials: CS
authors.lastname: Thompson
authors.forename: M E
authors.initials: ME
authors.lastname: Sullivan
authors.forename: D P
authors.initials: DP
authors.lastname: Mikhailidis
authors.forename: R J
authors.initials: RJ
authors.lastname: Morgan
mesh_terms: D000496:Alloxan; D000818:Animals; D001345:Autoradiography; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction; D011817:Rabbits; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000378:metabolism*; D001743:Urinary Bladder / Q000378:metabolism* / Q000503:physiopathology
chemical_list: D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D000496:Alloxan