title: The effects of combined free radical scavenger and sildenafil therapy on age-associated erectile dysfunction: An animal model.
abstract: BACKGROUND
  Aging results in erectile dysfunction that is partially attributed to decreased nitric oxide (NO) and increased free radical generation. Vitamin E enhances endothelial cell function and acts as a free radical scavenger; however, its benefits on erectile function in the elderly are unknown.
  
  
  OBJECTIVE
  The aim of the following study is to determine if Vitamin E alone, or in combination with the phosphodiesterase 5 inhibitor sildenafil, may improve erectile function and the NO signaling in a cohort of aged (13-15 month old) rats.
  
  
  METHODS
  Male Sprague-Dawley rats (n = 28) were divided based upon age into young (4-5 months old, n = 7) and aged (13-15 months old, n = 21) cohorts. Aged rats were treated with Vitamin E, sildenafil or a combination of both. Penile cavernosal and dorsal nerve tissues were evaluated for neuronal nitric oxide synthase (nNOS) and caveolin-1 expression. Erectile function was assessed through intra-cavernous pressure (ICP) recordings.
  
  
  RESULTS
  nNOS and cavoelin-1 were significantly decreased in aged rats compared with young controls. In aged rats, both Vitamin E and sildenafil partially recovered nNOS expression but when combined, a synergistic elevation in nNOS was observed. The significant decreases in ICP recorded in aged rats were improved with sildenafil; however, Vitamin E did not yield any additional improvements in ICP.
  
  
  CONCLUSIONS
  Diminished levels of nNOS and caveolin-1 are found in aged rats. When combined with sildenafil, Vitamin E synergistically increased nNOS expression. Since biochemical gains were not realized physiologically, other contributing factors likely exist.
authors.affiliation: Urology of Indiana, 12188-A North Meridian Street, Suite 200, Carmel, Indiana, 46032, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Kovac
authors.affiliation: Department of Urology, University of Western Ontario, St. Joseph's Hospital, London, Ontario, N6A 4V2, Canada.
authors.forename: Ling
authors.initials: L
authors.lastname: DeYoung
authors.affiliation: Dalhousie University, Halifax, Nova Scotia, Canada, McMaster University, Hamilton, Ontario, Australia.
authors.forename: Kyle J
authors.initials: KJ
authors.lastname: Lehmann
authors.affiliation: Department of Urology, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
authors.forename: Eric
authors.initials: E
authors.lastname: Chung
authors.affiliation: Department of Urology, University of Western Ontario, St. Joseph's Hospital, London, Ontario, N6A 4V2, Canada.
authors.forename: Gerald B
authors.initials: GB
authors.lastname: Brock
keywords: Aging; antioxidant; erectile dysfunction; impotence; nitric oxide; sildenafil; vitamin E