Metabolism of ATP (A), ADP (B), AMP (C) and adenosine (Ado, D) during a single pass of coronary circulation. Each substrate at 200 μM (0.3 ml) was added to the coronary perfusate after 20 min stabilization of the normal hearts. Metabolites in the coronary effluents of the first one minute fraction after injection of the substrate were measured by HPLC (Open columns; initial substrate, black columns; metabolites). Data are shown as percent of total metabolites collected. All values are means ± S.E.M (n = 13).