A Comparison of Methods for Estimating the Activity of the ATP-Sensitive Potassium Channel in Mitochondria Based on the Effect of ATP

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Abstract—Two methods for studying the functioning of the mitochondrial ATP-sensitive potassium channel, which plays an important role in cell physiology and especially in cardio- and neuroprotection, have been compared. It has been shown that the spectrophotometric method, which is most often used to study this channel and the influence of its modulators, has a number of limitations and mainly provides a qualitative assessment. A modification of this method is proposed, which makes it possible to obtain optical density changes recorded in a linear form that enables quantification of the change in the optical density and, as a consequence, allows a more accurate determination of the effect of various modulators. The concentration of ATP that causes half-maximal inhibition of the rate of potassium transport (ІС_{50_АТP}) in the rat liver mitochondria has been determined by two different methods. The ІС_{50_АТP}, as assessed by direct measurement with a potassium-selective microelectrode under 2,4-dinitrophenol-induced efflux of potassium, was 23 μM; it was 400 μM as assessed by the spectrophotometric method. The data we obtained suggest that recording of the 2,4-dinitrophenol-induced potassium efflux may be a more effective method for evaluating ATP-dependent transport of potassium ions in mitochondria.