Interactions of K+ATP channel blockers with Na +/K+-ATPase

oate (5-HD) and glyburide, are often used to study cross-talk between Na+/K+-ATPase and these channels. The aim of this work was to characterize the effects of these blockers on purified Na+/K+-ATPase as an aid to appro-priate use of these drugs in studies on this cross-talk. In contrast to known dual effects (activating and inhibitory) of other fatty acids on Na+/K+-ATPase, 5-HD only inhibited the enzyme at concentrations exceeding those that block mitochondrial K+ATP channels. 5-HD did not affect the ouabain sensitivity of Na+/K+-ATPase. Glyburide had both activating and inhibitory effects on Na+/K+-ATPase at concentrations used to block plasma membrane K+ATP channels. The findings justify the use of 5-HD as specific mitochondrial channel blocker in studies on the relation of this channel to Na+/K+-ATPase, but question the use of glyburide as a specific blocker of plasma membrane K+ATP channels, when the relation of this channel to Na+/K+-ATPase is being studied