Systemic and cavernous plasma levels of endothelin (1-21) during differentpenile conditions in healthy males and patients with erectile dysfunction

The role of the sympathetic adrenergic nerves in mediating the constant ton e of penile flaccidity and returning the erect penis to its flaccid state i s fairly well established. However, it is not yet known whether additional nonadrenergic transmitters are involved in this process. The peptide endoth elin-1 (ET-1) may be one of the factors contributing to such a control. Mor eover, it has been speculated by various authors that ET-1 might be involve d in the pathophysiology of erectile dysfunction. The present study was und ertaken to determine whether or not there is a difference in the courses of ET-1/-2 plasma levels registered in systemic and cavernous blood cavities taken from healthy males and patients with ED during different penile condi tions (flaccidity, tumescence/rigidity, detumescence). Thirty-two healthy a dult males and 25 patients were exposed to visual and tactile erotic stimul i in order to elicit penile tumescence and, in the group of healthy volunte ers, rigidity. Whole blood was aspirated from the corpus cavernosum and the cubital vein, and ET-1/-2 was determined in plasma aliquots by means of an enzyme-linked immunoassay (ELISA). Mean systemic and cavernous plasma level of ET-1/-2 in blood samples obtain ed from the volunteers was 0.2-0.7 fmol/ml. In the healthy males, no change s in ET-1/-2 levels were observed in the systemic and cavernous blood durin g penile tumescence, rigidity and detumescence. In the group of patients, m ean plasma ET-1/-2 levels in the phase of penile flaccidity and detumescenc e were found to be higher in the systemic circulation than in the cavernous blood (flaccidity: 0.52 +/- 0.38 fmol/ml vs. 0.48 +/- 0.46 fmol/ml, respec tively; detumescence: 0.53 +/- 0.33 fmol/ml vs. 0.27 +/- 0.11 fmol/ml, resp ectively). No differences in the plasma courses of ET-1/-2 were found betwe en patients with an organogenic and psychogenic etiology of ED. In the phas e of detumescence, the mean ET-1/-2 level was lower in the cavernous blood cavities taken from the patients than in the samples obtained from the heal thy males. Our study revealed a difference in the profiles of ET-1/-2 registered in th e cavernous blood of healthy subjects and patients with erectile dysfunctio n. Nevertheless, since this difference seems to be of no physiological sign ificance, our data counteract the hypothesis of an ultimate importance of E T-I in the control of penile flaccidity and detumescence and do not support speculations regarding an involvement of ET-1 in the pathophysiology of er ectile dysfunction.