The effect of adrenaline on the electrogenic Na+ pump in cardiac muscle cells.

Electrogenic Na+ pump currents during K+-activated hyperpolarizations of bullfrog atrium muscle fibres are increased by adrenaline. The log dose-response relation between these currents and activating K+ concentrations is expressed by a sigmoidal curve, which is shifted in parallel to the left by adrenaline. It is suggested that adrenaline increases the rate of Na+ extrusion without increasing the Na/K coupling ratio and total number of pumping sites.