Levels of l-arginine and l-citrulline in patients with erectile dysfunction of different etiology

Nitric oxide is a physiologic signal essential to penile erection. l-citrulline (l-Cit) is converted into l-arginine (l-Arg), the precursor from which nitric oxide is generated. The level of l-Arg and l-Cit in the field of male sexual function remains relatively underexplored. The aim of the study was to evaluate the level of serum l-Arg and of l-Cit in a group of patients with erectile dysfunction. Diagnosis and severity of erectile dysfunction was based on the IIEF-5 and its etiology was classified as arteriogenic (A-ED), borderline (BL-ED), and non-arteriogenic (NA-ED) with penile echo-color-Doppler in basal condition and after intracaversous injection of prostaglandin E1. Serum l-Arg and l-Cit concentrations were measured by a cation-exchange chromatography system. l-Arg and l-Cit levels of men with A-ED were compared with those of male with BL-ED and NA-ED. Median level of l-Arg and l-Cit in 122 erectile dysfunction patients (41 A-ED, 23 ED-BL, 58 NA-ED) was 82.7 and 35.4\ua0\u3bcmol/L, respectively. l-Arg and l-Cit levels in control patients were not significantly different (p\ua0=\ua00.233 and p\ua0=\ua00.561, respectively) than in total erectile dysfunction patients. l-Arg and l-Cit levels in control patients were significantly higher (p\ua0\ua00.50) was observed in controls and in both BL-ED and NA-ED patients. Patients with severe/complete-erectile dysfunction (IIEF-5\ua0\ua00.3) but without reaching the statistical significance. Our study shows that a significant proportion of erectile dysfunction patients have low l-Arg or l-Cit level and that this condition is more frequent in patients with arteriogenic etiology. Low levels of these nitric oxide synthase substrates might increase the erectile dysfunction risk by reducing the concentration of nitric oxide