Effects of micromolar concentrations of manganese, copper, and zinc on alpha(1)-adrenoceptor-mediating contraction in rat aorta

To determine the influences of the Mn, Cu, and Zn on alpha (1)-adrenoceptor (AR)-mediated vasoconstriction, we investigated their effects on vasoconst riction produced by the alpha (1)-AR agonist phenylephrine in isolated ring s of rat thoracic aorta. The cumulative concentration-contraction curves fo r phenylephrine were obtained in the absence and presence of Mn (0.3, 1, 3 muM), Cu (1, 10, 16 muM), and Zn (0.3, 1, 10 muM). Mn, Cu, and Zn each inhi bited phenylephrine-mediated contraction in a dose-dependent manner. The ma ximal phenylephrine-induced contraction was significantly reduced by the pr etreatment of the arterial rings with 10 and 16 muM Cu (p <0.05). The resul ts suggest that variations in the plasma concentrations of metal might lead to changes in alpha (1)-AR-mediated constrictive response.