Modulation of myocardial activity by extracellular ATP.

Extracellular ATP, at micromolar concentration, induces multiple functional changes in cardiac cells. Stimulation of P(2) purinoceptors is associated with Ca current increase and positive inotropic effect. On rapid application, ATP triggers membrane depolarization by activating a Cl conductance and by inducing an acidification following Cl-HCO(3) exchanger stimulation. Both effects might lead to cardiac arrhythmias following ATP release under pathophysiologic conditions.