Adenosine triphosphate-sensitive potassium channels in the cardiovascular system

ATP is normally available in cells at millimolar concentrations and is ''buffered'' by intracellular pools of other high-energy phosphates, such as creatine phosphate. Thus intracellular [ATP] ([ATP](i)) may seem an unlikely candidate for a regulatory signal inside cells. Recent evidence suggests, however, that [ATP](i) regulates the behavior of a class of potassium (K(ATP)) channels that are found throughout the cardiovascular system. K(ATP) channels are present in cardiac, skeletal, and vascular smooth muscle. The channels are inhibited by micromolar [ATP](i), and this inhibition is relieved by micromolar [ADP](i). We present evidence in support of the idea that variations of [ATP](i) and [ADP](i), even within normal concentration ranges, may influence cellular function in the heart and vascular system via a direct action on the K(ATP) channel. Furthermore, very specific modulators of K(ATP) channel activity are available. We discuss the mechanism of action of these agents and their interaction with endogenous modulators and consider their potential roles in cardiovascular therapy.