6‐Nitrodopamine is an endogenous mediator of the rabbit corpus cavernosum relaxation
Antonio Tiago Lima, José Britto‐Júnior, Manoel Odorico Moraes, Maria Elisabete A. Moraes, Adriano Fregonesi, Fabíola Z. Monica, Edson Antunes, Gilberto De Nucci- Urology
- Endocrinology
- Reproductive Medicine
- Endocrinology, Diabetes and Metabolism
Abstract
Background
6‐Nitrodopamine (6‐ND) is a novel endogenous catecholamine that has a potent relaxant action on vascular smooth muscle in vitro.
Objectives
To evaluate the basal release of 6‐ND and noradrenaline from rabbit‐isolated corpus cavernosum (RbCC) and its relaxing action on this tissue.
Methods
Rabbit corpus cavernosa were dissected and suspended in a 5‐mL organ bath containing oxygenated Krebs‐Henseleit's solution. 6‐ND and noradrenaline release was quantified by liquid chromatography coupled to tandem mass spectrometry. The relaxant activity of 6‐ND was assessed in RbCC strips pre‐contracted with endothelin‐1 (10 nM).
Results
Rabbit corpus cavernosum presented basal release of both 6‐ND (2.9 ± 0.8 ng/mL, n = 12) and noradrenaline (1.7 ± 1.3 ng/mL, n = 12). The 6‐ND release was reduced by pre‐treatment with Nω‐nitro‐
Discussion and conclusion
6‐Nitrodopamine is the most potent endogenous relaxant agent in RbCC ever described and represents a novel mechanism by which NO causes corpus cavernosum smooth muscle relaxation. The finding that 6‐ND acts as a truly selective dopamine D2‐receptor antagonist indicates that the balance of dopamine and 6‐ND release/synthesis may be the main mechanism that modulates corpus cavernosum smooth muscle tonus in vivo.