ADP promotes diazoxide activation of native cardiac KATP channels. (A) Current tracing recorded at −60 mV in an inside-out patch excised from a guinea pig ventricular myocyte. (B) Normalized current observed in eight patches in the presence of ADP (100 μM), diazoxide (300 μM), or both. To reduce errors because of low channel activity, mean current was estimated from nPo values (n, number of channels; Po, open probability) obtained by analysis of gating transitions (28).