Effect of N-(biphenylyl-methyl)imidazole, a type 1 angiotensin II receptor inhibitor, on the contractile function of the rat corpus cavernosum

Plasma levels of angiotensin II during different penile conditions in the cavernous and systemic blood of healthy men and patients with erectile dysfunction

OBJECTIVES

To detect changes in plasma levels of angiotensin II (Ang II) under different functional conditions of the penile erectile tissue in the cavernous and systemic blood of patients with erectile dysfunction (ED) and compare them with the course of Ang II in healthy male subjects. It has been shown that the mammalian corpus cavernosum produces and secretes physiologically relevant amounts of the vasoconstrictive peptide Ang II and that intracavernosal injection of Ang II terminates penile erection in the dog. Thus, we speculated whether a dysregulation in the secretion or degradation of Ang II might contribute to the manifestation of ED.

METHODS

Thirty-four healthy adult men and 48 patients with ED of either organogenic or psychogenic etiology were exposed to visual and tactile erotic stimuli to elicit penile tumescence and, in the group of healthy subjects, rigidity. Whole blood was simultaneously aspirated from the corpus cavernosum and the cubital vein during the different functional conditions of the penis. Ang II plasma levels were measured using a radioimmunoassay.

RESULTS

In healthy men, the Ang II levels in the cavernous plasma increased from 22.1 +/- 7.1 pg/mL in the phase of penile rigidity to 27.9 +/- 10 pg/mL in the detumescence phase. In the peripheral plasma, the Ang II levels were 17.2 +/- 6.2 to 19.5 +/- 6.5 pg/mL over the respective penile stages. The courses of Ang II registered in the patients were similar to those detected in the healthy men. In the patients and healthy men, systemic Ang II levels were found to be lower than the concentrations detected in the cavernous blood. In the group of organogenic patients, the Ang II levels during penile flaccidity in the systemic and cavernous blood were higher than those registered in the blood samples taken from the healthy men.

CONCLUSIONS

Our results suggest that cavernous smooth muscle tone is, in part, balanced by Ang II-induced contraction and that Ang II might be involved in the initiation of penile detumescence in men. That Ang II plasma levels are generally elevated in the systemic and cavernous blood of patients with an organogenic etiology of ED may hint at the significance of Ang II in the pathophysiology of ED. Since the tissue and plasma levels of Ang II are regulated by the activity of angiotensin-converting enzyme, there might be a rationale for the use of angiotensin-converting enzyme inhibitors in the treatment of vasculogenic ED.