REVIEWS: The Potential Role of the Heme Oxygenase/Carbon Monoxide System in Male Sexual Dysfunctions


Rany Shamloul, MD, Queen's University, Pharmacology, Kingston, ON, Canada. Tel: 6135336432; Fax: 6135336412; E-mail:


Introduction.  Recently there has been a growing interest regarding the role of carbon monoxide (CO) and its precursor, heme oxygenase (HO) in mediation of penile erection and their potential roles as molecular targets in treatment of erectile dysfunction.

Aim.  To review the available literature on the role of the HO/CO system in male sexual dysfunctions.

Methods.  This review will begin by a discussion of the physiology of the HO/CO system followed by a detailed assessment of the literature examining the role of HO/CO system in male sexual dysfunctions.

Main Outcome Measures.  The effect of HO/CO system on penile erection, ejaculation, and priapism.

Results.  Most of the studies attempting to investigate the role of HO/CO in male sexual functions focused on penile erection. The majority of these studies did report a significant positive effect of the HO/CO system on penile erection. However, none of these studies examined the role of HO/CO system in aging animals; aging being considered the most important risk factor for ED. Furthermore, only one study tested the role of HO/CO system in erectile function. The important observation that HO-2 deficient mice have low bulbospongiosus muscle activity deserves extensive research on the value of HO inhibition in the treatment of premature ejaculation. Data from the only study on low-flow priapism and HO suggests that HO-1 is involved in the paradigm of low-flow priapism.

Conclusions.  The HO/CO system may have an important role in many male sexual functions. Extensive research is needed to precisely delineate the extent to which the HO/CO system plays in the physiology and pathophysiology of male sexual dysfunctions. Shamloul R. The potential role of the heme oxygenase/carbon monoxide system in male sexual dysfunctions. J Sex Med 2009;6:324–333.