Coenzyme Q10 attenuates cyanide-activation of the ATP-sensitive K+ channel current in single cardiac myocytes of the guinea-pig

The effect of coenzyme Q10 (CoQ10) on the cyanide (CN−)-induced ATP-sensitive K+ channel current (KATP) was examined in single atrial myocytes, using the patch clamp technique. Superfusion of the cells with a CN−/low glucose bathing solution induced an outward current in the whole-cell clamp condition. Glibenclamide (1 μM) abolished this current, indicating that the current was carried through the KATP channel. After steady-state activation by CN−, pinacidil (a KATP channel opener, 300 μM) failed to further increase the current. In cell-attached patches, CN−, when applied to the bath, induced bursting openings of an 80 pS channel (the KATP channel). In cells preincubated for 30 min in a solution containing CoQ10 (100 μg/ml), CN−-activation of the KATP channel was markedly attenuated both at the whole cell and at the single channel level. At the steady-state effect of CN− in CoQ10-treated cells, pinacidil (300 μM) activated the current to the maximum level achieved by CN− in the control cells. These results suggest that CoQ10 reduces in the CN−-induced KATP current not by affecting the channel itself but by preventing depletion of intracellular ATP caused by CN−.