Myocytes by Free Fatty Acids

Using rat ventricular cells, we studied the actions of free fatty acids and their ability to modulate the ATP-sensitive K' channel and to activate a new type of ATP-insensitive K' channel previously identified in rat atrial cells. Perfusion of the cytoplasmic face of the membrane with unsaturated fatty acids (10-50 ,M) such as arachidonic, linoleic, and eicosatrienoic acids inhibited the ATP-sensitive K' channel almost completely; lysophospholipids also markedly inhibited this channel. Inhibition was due to decreases in the frequency and the burst duration of channel openings. Arachidonic acid activated the ATP-insensitive K' channel with an outwardly rectifying property. Since the level of free fatty acids rises after longer periods of ischemia, we speculate that the ATP-insensitive K' channel contributes to the late or secondary phase of extracellular K' accumulation. (Circulation Research 1990;67: 1040-1046)