The effect of adenosine on cardiac cells in culture

Chronotropic effect of 5 × 10 −6 m to 5 × 10 −5 m-adenosine on beating rat heart cells in culture was demonstrated. Concomitant with the increased rate of rhythmic contractions was a 50% increase in the intracellular ATP concentration, a net synthesis of c. 15 nmol ATP/mg protein. This net change in concentration was a result of a new high steady state of ATP synthesis and not of a transphosphorylation from phosphorylcreatine, as the latter remained at control levels. The rhythmic contractions and the increased ATP synthesis in the presence of adenosine were inhibited by oligomycin + 2-deoxyglucose and 1-fluoro-2,4-dinitrobenzene The excitability of the cardiac cell membrane correlates with a continuous synthesis of ATP.