The role of adrenergic receptors in Ni2+-induced coronary vasoconstriction

The possible involvement of adrenergic receptors in nickel ion (Ni2+)-induced coronary vasoconstriction was studied on isolated perfused rat hearts and on isolated canine coronary artery strips. The experiments on both models showed that (i) alfa-adrenergic blockade by phenoxybenzamine or phentholamine caused only partial depression of Ni2+-induced coronary vasoconstriction: (ii) beta-adrenergic receptor blockade by propranolol totally prevented Ni2+-action, and (iii) Ni2+ (1 microM) caused significant inhibition of coronary vasodilatation induced by isoproterenol. The experimental results indicate that alfa-adrenoceptors play minor role (if any) in the coronary action mechanism of Ni2+ but it may be mediated by beta-adrenergic mechanisms. Nickel was found to alter the reactivity of coronary beta-adrenoceptors suggesting a possible modulatory role of this trace metal in coronary adrenergic mechanisms.