ATP‐sensitive K channels in heart muscle Spare channels

Abstract

We show that ATP-sensitive K⁺ channels of excised inside-out membrane patches of rat ventricular myocytes show considerable variation in their sensitivity to ATP. In 102 different membrane patches IC₅₀ values ranged from 9 to 580 μM ATP and Hill coefficient from 1% to 6.41% of patches showed openings of ATP-sensitive K⁺ channels in the presence of 1 mM ATP. These results considerably widen the range of internal ATP concentrations over which one might expect activation of the ATP-sensitive K⁺ current in cardiac myocytes.