title: An in vitro method of studying functional responses of penile resistance arteries under isobaric conditions.
abstract: OBJECTIVE
  We developed an in vitro method that allows us to study the physiopharmacological responses of penile resistance arteries under isobaric conditions.
  
  
  METHODS
  Second to third order penile resistance arteries (internal diameter 170 to 210 microm) were mounted in a pressure myograph and cannulated at each end with small glass cannulas (tip external diameter 150 to 180 microm). Internal diameter was continuously recorded and monitored under an intraluminal pressure of 60 mm Hg.
  
  
  RESULTS
  Noradrenaline (0.1 to 0.3 microM) induced a decrease in the luminal diameter of the penile arteries, ie vasoconstriction. This effect was reversed by 1 microM acetylcholine, 1 microM prostaglandin E1 (PGE1) and 1 nM to 1 microM sildenafil citrate. Furthermore, the vasodilatation induced by sildenafil was compared by artery internal diameter values under isometric and isobaric conditions. Although the mean potency of this drug +/- SEM, expressed in pD2, was higher in 5 isometric (7.60 +/- 0.04) than in 4 isobaric (7.03 +/- 0.20) preparations (p <0.05), the slope of the curve was lower in 4 isobaric (0.49 +/- 0.02) than in 5 isometric (1.34 +/- 0.11) studies (p <0.01).
  
  
  CONCLUSIONS
  Under isobaric conditions all vasoactive agents tested inhibited the noradrenaline induced vasoconstriction. Furthermore, the vasodilatory effect of PGE1 beyond baseline diameter could suggest an inhibitory effect of PGE1 on spontaneous myogenic tone. On the other hand, the effect of sildenafil was more potent under isometric than under isobaric conditions. However, the lower slope of the curve under isobaric conditions suggests that the pressure myograph could be a more suitable in vitro model for the study of the activity of penile resistance arteries, and so isobaric conditions correspond more closely to the in vivo situation.
authors.affiliation: Departamento de Fisiología, Facultad de Farmacia, Universidad Complutense, Madrid, Spain. lrivera@farm.ucm.es
authors.forename: L Rivera
authors.initials: LR
authors.lastname: de los Arcos
authors.forename: D
authors.initials: D
authors.lastname: Prieto
authors.forename: A C
authors.initials: AC
authors.lastname: Martínez
authors.forename: S
authors.initials: S
authors.lastname: Benedito
authors.forename: M
authors.initials: M
authors.lastname: Hernández
authors.forename: A
authors.initials: A
authors.lastname: García-Sacristán
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology; D006736:Horses; D066298:In Vitro Techniques; D008297:Male; D010413:Penis / Q000098:blood supply* / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology; D011687:Purines; D000068677:Sildenafil Citrate; D013450:Sulfones; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate