Purpose: Endothelial P2y purinoceptor stimulation is known to induce vasodilatation mediated by NO release from endothelial cells. We examined the effect of a potent P2y agonist, adenosine-5'-O-(2-thiodiphosphate) (ADPβS), on human corporal cavernosal strips and its dependence on a functional endothelial lining. Materials and Methods: The preparations mounted in isometric conditions were precontracted by noradrenaline (NA) at a concentration of 0.1 μM. Increasing concentrations of ADPβS from 1 μM to 100 μM were added in the presence and absence of a functional endothelium or in the presence and absence of an NO synthase inhibitor and a selective P2y antagonist. Acetylcholine (Ach)-induced relaxation was used in each experiment for control. Results: In human precontracted corporal cavernosal strips with a functional endothelium (relaxed by acetylcholine) ADPβS induces a dose-dependent relaxation with maximal relaxation of 45.5 ± 5.0% and an EC50 of 11.7 μM. The relaxant effect of ADPβS was reduced by 77.1 ± 7.0% by reactive blue 2 (20 μM)(a P2y antagonist). L-NAME (L-Nitro Arginin Methyl Ester), an NO synthase inhibitor (100 μM), reduced Ach- and ADPβS- induced relaxations by 86.59 ± 3.24% and 86.83 ± 0.5% respectively. Ach- and ADPβS- induced relaxations were significantly inhibited after dislodging of the endothelial lining of the corporal cavernosal strips, 90.11 ± 6.2% and 87.1 ± 5% respectively. Conclusions: Human corporal cavernosal strips can be relaxed by stimulation of P2y purinoceptors via NO release. This relaxation is an endothelium-dependent mechanism. Purines may be implicated in physiological erection in man.
- Human corpus cavernosum smooth muscle
- Nitric oxide
- P2y purinoceptors
- Penile erection