Changes in intracellular ion activities induced by adrenaline in human and rat skeletal muscle

To study the stimulating effect of adrenaline (ADR) on active Na+/K+ transport we used double-barrelled ion-sensitive micro-electrodes to measure the activities of extracellular K+ (aKe) and intracellular Na+ (aNai) in isolated preparations of rat soleus muscle, normal human intercostal muscle and in one case of hyperkalemic periodic paralysis (h.p.p.). In these preparations, bath-application of ADR (10(-6) M) resulted in a membrane hyperpolarization and transient decreases aKe and aNai which could be blocked by ouabain (3 x 10(-4) M). In the h.p.p. muscle a continuous rise of aNai induced by elevation of aKe to 5.2 mM could be stopped by ADR. In addition, the intracellular K+ activity (aKi), the free intracellular Ca2+ concentration (pCai) and intracellular pH (pHi) were monitored in rat soleus muscle. During ADR aKi increased, pHi remained constant and intracellular Ca2+ apparently decreased. In conclusion, our data show that ADR primarily stimulates the Na+/K+ pump in mammalian skeletal muscle. This stimulating action is not impaired in the h.p.p. muscle.