Nickel inhibits β-1 adrenoceptor mediated activation of cardiac CFTR chloride channels

► We report the block of the β-adrenoceptor-activated cardiac CFTR Cl− current by Ni2+. ► Extracellular Ni2+ inhibits the current activated by β1-adrenoceptors in a concentration-dependent manner. ► The action of Ni2+ is insensitive to β2-blockade. ► Ni2+ does not affect the β-adrenoceptor-activated current from the intracellular side. ► The data are consistent with an action of Ni2+ at the β1-adrenoceptor from the external side.