Physiological heart activation by adrenaline involves parallel activation of ATP usage and supply Available to Purchase

During low-to-high work transition in adult mammalian heart in vivo the concentrations of free ADP, ATP, PCr (phosphocreatine), P_i and NADH are essentially constant, in striking contrast with skeletal muscle. The direct activation by calcium ions of ATP usage and feedback activation of ATP production by ADP (and P_i) alone cannot explain this perfect homoeostasis. A comparison of the response to adrenaline (increase in rate-pressure product and [PCr]) of the intact beating perfused rat heart with the elasticities of the PCr producer and consumer to PCr concentration demonstrated that both the ATP/PCr-producing block and ATP/PCr-consuming block are directly activated to a similar extent during physiological heart activation. Our finding constitutes a direct evidence for the parallel-activation mechanism of the regulation of oxidative phosphorylation in heart postulated previously in a theoretical way.