Physiology of erectile function.
BACKGROUND
There are numerous investigations concerning the balance and interactions between relaxant and contractile factors regulating penile smooth muscle (arterial and trabecular) tone, the determinant of penile flaccidity or erection. Enhanced knowledge of erectile physiology may improve management of men with erectile dysfunction. Aim. To provide state-of-the-art knowledge on the physiology of erectile function.


METHODS
An international consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a two-year period. Concerning the physiology of erectile function and pathophysiology of erectile dysfunction committee, there were seven experts from five countries.


METHODS
Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.


RESULTS
Key roles in the mechanism determining the tone of penile smooth muscle are played by the rise of the intracellular concentration of free calcium and the sensitivity of the contractile machinery to calcium, endothelial health, endothelium-derived nitric oxide, endothelium-derived hyperpolarizing factor (EDHF), neuronal nitric oxide, cyclic guanosine monophosphate-dependent protein kinase and phosphodiesterase type 5.


CONCLUSIONS
A number of new mechanisms have been identified for the local regulation of penile smooth muscle contractility and therefore penile erection. Molecules participating in these pathways can be considered targets for the development of new treatments to treat erectile dysfunction.
Sáenz de Tejada
Iñigo
I
Fundacion para la Investigacion y el Desarrollo en Andrologia, Madrid, Spain. isdtejada@terra.es
Angulo
Javier
J
Cellek
Selim
S
González-Cadavid
Nestor
N
Heaton
Jeremy
J
Pickard
Robert
R
Simonsen
Ulf
U
D015106:3',5'-Cyclic-GMP Phosphodiesterases; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D007172:Erectile Dysfunction / Q000503:physiopathology; D006801:Humans; D007391:International Cooperation; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology; D010100:Oxygen / Q000502:physiology; D010410:Penile Erection / Q000502:physiology*; D010727:Phosphoric Diester Hydrolases / Q000502:physiology; D014661:Vasoconstriction / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
D017869:Cyclic GMP-Dependent Protein Kinases; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; D010100:Oxygen