Involvement of β 3 -Adrenergic Receptor Activation in Human Corpus Cavernosum Function

Abstract

β3 adrenergic receptors are extensively studied, and in animal model it was demostrated their involvement in the vasorelaxation of smooth muscle cells. However the precise role and their exact distribution in human body is almost unknown. We studied the presence of β3 adrenergic receptors in human corpus cavernosum and the pathways involved in their activation:

Materials and Methods

Using strips isolated from human corpus cavernosum obtained from transsexual surgical procedures, we tested this receptors with a specific agonist BRL-37344 (10^–5 −10^–8) to understand their precise role. Removing endothelium and using L-NAME (100 μM), we tested the involvement of NO in the pathways of activation of this receptors.

Results

We demostrated the presence of β3 adrenergic receptors in the human corpora cavernosa and their mainly localization in the smooth muscle cells of vascular vessels. Our results dimostrated, making a stimulation with BRL-37344, that exists a mechanism of smooth muscle relaxation concentration-dependent. This relaxation is endothelium-indipendent too, like we showed removing it or using L-NAME. The vasorelaxation induced by BRL-37344 is realized by the increase of cGMP level of 7-fold like it was dimostrated by ELISA. Moreover the use of SR-59230A, an antagonist of β3 adrenergic receptors, removes the relaxant effect.

Conclusions

The vascular smooth muscle in human corpus cavernosum possesses tonic or continuous β3-adrenergic receptor activity (mediating relaxation), as suggested by the vasoconstrictor effect that results from selectively antagonizing the β3-adrenergic receptors. The presence of β3-adrenergic receptors in human corpus cavernosum and their possible involvement in promoting erectile function via cGMP but NO-indipendent, may open new approaches to develop new treatment of E.D.