Stretch-activated K<SUP>&#8290;</SUP> Channels in Rat Atrial Myocytes

Stretch-activated K<SUP>&#8290;</SUP> Channels in Rat Atrial Myocytes

Mechanical stimuli to the cardiac myocytes initiate many biochemical and physiological events. Stretch-activated cation channels have been suggested to mediate these events. In this study, cell-attached and inside-out excised-patch clamp methods were used to identify stretch-activated cation channels in adult rat atrial myocytes. Channel openings were increased in cell-attached configuration when negative pressure was applied to the pipette, and also in inside-out excised patches by negative pressure. The channel was not permeable to Cl<SUP>&#8291;</SUP>, Na<SUP>&#8290;</SUP> and Cs<SUP>&#8290;</SUP>, but selectively permeable to K<SUP>&#8290;</SUP>, and the degree of activation was dependent on the magnitude of negative pressure (full activation at <FONT FACE= 바탕 >∼ &#8291;50 mmHg). In symmetrical 140 mM KCl, the slope conductance was 51.2&#8273;3 pS between the potentials of &#8291;80 and 0 mV and 55&#8273;6 pS between 0 and &#8290;80 mV (n=5). Glibenclamide (100<FONT FACE= 바탕 >μM) or ATP (2 mM) failed to block the channel openings, indicating that it is not ATP-sensitive K<SUP>&#8290;</SUP> channel. Arachidonic acid (30<FONT FACE= 바탕 >μM), which has been shown to activate a K<SUP>&#8290;</SUP> channel cooperatively with membrane stretch, did not affect the channel activity. GdCl<SUB>3</SUB> (100<FONT FACE= 바탕 >μM) also did not alter the activity. These results demonstrate that the mechanical stretch in rat atrial myocytes activates a novel K<SUP>&#8290;</SUP>-selective cation channel, which is not associated with other K<SUP>&#8290;</SUP> channels such as ATP-sensitive and arachidonic acid-activated K<SUP>&#8290;</SUP> channel.