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Título

BASAL RELEASE OF 6-CYANODOPAMINE FROM RAT ISOLATED VAS DEFERENS AND ITS ROLE ON THE VAS DEFERENS CONTRACTILITY

Resumo

6-Cyanodopamine is released from rabbit isolated heart. However, it is not known whether this novel catecholamine presents any biological activity. Here it was evaluated whether 6-cyanodopamine was released from rat isolated vas deferens and its effect on this tissue contractility. Basal release of 6-bromodopamine, 6-nitrodopa, 6-nitrodopamine, 6-cyanodopamine, and 6-nitroadrenaline from vas deferens were quantified by LC-MS/MS. Electric-field stimulation (EFS) and concentration-response curves to noradrenaline, adrenaline, and dopamine of the rat isolated epididymal vas deferens (RIEVD) were performed in the absence and presence of 6-cyanodopamine. Expression of tyrosine hydroxylase and S100 was assessed by immunohistochemistry.

The rat isolated vas deferens release both 6-cyanodopamine and 6-nitrodopamine. Pre-incubation with tetrodotoxin, had no effect on the release of 6-cyanodopamine, but it virtually abolished 6-nitrodopamine release. 6-Cyanodopamine contracted RIEVD only at 1mM, but significantly potentiated the contractions induced by both noradrenaline and EFS at 1 nM. At 10 and 100 nM, 6-cyanodopamine also significantly potentiated the RIEVD contractions induced by adrenaline and dopamine. The potentiation of both noradrenaline and adrenaline contractions by 6-cyanodopamine was present in tetrodotoxin-pretreated tissues. Co-incubation of 6-cyanodopamine (100 pM) with 6-nitrodopamine (10 pM), caused significant leftward shifts and increased maximal responses of the concentration-response curves to noradrenaline, even in the presence of tetrodotoxin. Immunohistochemistry on RIEVD revealed the presence of tyrosine hydroxylase in both the cytoplasm of epithelial cells of the mucosae and in the nerve fibers.

The identification of epithelium-derived 6-cyanodpamine and its remarkable synergism with catecholamines indicate that epithelial cells may regulate the smooth muscle contractility.

Palavras Chave

tandem mass spectrometry; smooth muscle tonus; ejaculation;