ATP-sensitive potassium channels and cardiac protection (part 4)
The ATP molecule acts on two sites of the Katp channel (Figure1). Opening of the channel is inhibited by ATP binding to the ‘regulatory site’. At the second, ‘phosphorylation site’, Mg-ATP complex is hydrolyzed. After ATP withdrawal, the initially full activation of the channel gradually wanes (termed the ‘run down’ phenomenon), obviously due to spontaneous dephosphorylation because this phenomenon may be reversed in the presence of Mg-ATP complex . ([Mg2+]i in the physiological range is a prerequisite for the effects of phosphonucleotides in general.)
The properties of Katp channels from various tissues differ merely in their sensitivity to the inhibitory effect of ATP, to Ca2+ and to some drugs, as well as the selectivity to K+. Based on these differences, Katp channels were classified as types 1 to 5 (reviewed in 11). Katp channels from all striated muscles and pancreatic beta-cells are type 1.
Figure 1 Diagram representing ATP-sensitive potassium channel (Katp) and the main constituents of its regulation. The closed state (A) prevails at physiological conditions and the open state (B) during ATP deficiency. Ai Adenosine receptor; a, P, у G protein subunits; AD Adenosine. Modified from reference 11 If you are looking for best deals on medications you need and would like to purchase cheap ventolin inhalers right now, you have got to visit the best pharmacy on the internet offering the full range of services.