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An. R. Acad. Nac. Farm., 2007, 73 (4): 963-985

Revisión

Physiology of penile vasculature: endothelium
and erectile dysfunction

Recibido el 19 de octubre de 2007

DOLORES PRIETO Y ALBINO GARCÍA SACRISTÁN*
Departamento de Fisiología, Facultad de Farmacia, Universidad

Complutense, 28040-Madrid, Spain.

ABSTRACT

Erectile dysfunction (ED) is considered as an early sign of endothelial
dysfunction and cardiovascular disease. The present review gives an overview of
the physiological factors involved in the regulation of penile vasculature with
special regard to the role of the vascular endothelium. Sympathetic nerves maintain
flaccidity and mediate detumescence through the release of the vasoconstrictor
noradrenaline that down-regulates its own release and that of nitric oxide (NO).
The sympathetic cotransmitter neuropeptide Y (NPY) enhances noradrenergic
vasoconstriction and also elicits non-NO endothelium-dependent relaxations. a1-
adrenoceptor-mediated vasoconstriction involves Ca2+ influx through L-type and
receptor-operated (ROC) Ca2+ channels, as well as Ca2+ sensitization mechanisms
mediated by protein kinase C (PKC), tyrosine kinases (TKs) and Rho kinase (RhoK)
in penile small arteries. Rho kinase (RhoK) can regulate Ca2+ entry in addition to
its role in Ca2+ sensitization. Vasodilatation of penile arteries and large veins during
erection is mediated by neurally-released NO and the subsequent increased arterial
inflow and shear stress activates endothelial NO production through Akt-
phosphorylation of endothelial NO synthase (eNOS). cyclic guanonin 3´-
monophosphate (cGMP)-stimulated K+ efflux through Ca2+-activated (KCa) and
voltage-dependent Ca2+ (Kv) channels is involved in the NO relaxant responses of
penile arteries and veins, respectively. Phoshodiesterase type 5 (PDE5) inhibitors
are potent vasodilators of penile arteries and increase the effects of basally released
endothelial NO. Endothelium-dependent relaxations of penile small arteries include
an endothelium-derived hyperpolarizing factor (EDHF)-type response which is

* e mail: agarsac@farm.ucm.es

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