[Flow-dependent dilatation of the cavernous artery. A potential test of penile NO content]

Nitric oxide (NO) is now considered as the main contributor to elicit and maintain erection. It is also established that flow-dependent dilatation of conduit arteries is mediated by NO. The present study was designed to verify the possibility of assessing the penile NO content when measuring the post occlusive vasodilatation of the cavernous arteries.

Ninety five subjects, 22 with normal erections (control group) and 73 with various degrees of erectile dysfunction (ED), measured with the international index of erectile function (IIEF) and erectile activity index (IAE). Multidisciplinary evaluation helped to separate two subgroups: mainly organic (n=47) and mainly psychologic (n=26). The diameter of one of the two cavernous arteries was measured by duplex-scan before and after a five-minute complete occlusion of penile vascular flow. The criterion retained was the maximum percentage of dilatation achieved within 45 to 90 sec after the release of the occlusion. Means were compared in the clinical groups. Influences of IIEF, IAE, age, arterial risk factors, preocclusive diameter of the artery, testosterone and DHEA levels were evaluated.

The mean percentage of increase in the control group was 65.2 +/- 26.3% vs 34.9 +/- 34.9% for the ED group (p=0.0003). The psychologic subgroup with 68.2 +/- 40% was similar to the control group as opposed to the organic group which showed a highly-significant difference (16.4 +/- 8.4; p=0.0001). In the control group and the psychological sub-group, subjects with arterial risk factors exhibited a less pronounced response (53.7 +/- 22) as compared to those free of any risk factors (80.3 +/- 30%) p=0.007. Age (r=0.29), preocclusion arterial diameter (r=0.3) and DHEA-S (r=0.56) as well as IIEF and IAE were correlated with the magnitude of the reaction. Sensitivity (100%) and specificity (92%) have been achieved in discriminating organic from psychologic DE.

Flow-dependent vasodilatation of the cavernous artery is extremely strong. It is much stronger in control subjects and in patients with predominantly psychological ED. An increase of 30% seems to be a critical level since only patients in the organic group were below that level. Thus, organic ED seems to be linked to the decrease of NO production by the cavernous bodies. If these results were confirmed post occlusive vasodilatation of the cavernous artery might be proposed as a fully non-invasive diagnostic and prognostic test in the study of ED. We propose to call it PNORT (penile NO release test).