Figure 6. Effects of ADP in the absence of CP.

After 10 min equilibration in the presence of 10 mm CP, [Ca²⁺] remained constant when the flow was stopped (left). Withdrawal of CP resulted in a transient Ca²⁺ efflux. In the continued absence of CP, the [Ca²⁺] increased markedly when the flow was stopped (middle). Subsequent introduction of 2 mm ADP resulted in a further transient Ca²⁺ efflux (right). However, when perfusion was then stopped, the Ca²⁺ efflux was markedly reduced relative to that obtained in the absence of CP and P_i.