ATP-sensitive potassium channels and cardiac protection (part 6). Katp CHANNEL INHIBITORS AND OPENERS
There is much evidence to support the idea that Katp channels are modulated by endogenous ligands, first by adenosine, the terminal product of ATP hydrolysis under hypoxic or ischemic conditions. Adenosine binds to purinergic A1 receptor and exerts its intracellular action by means of a G protein. Consequently, the affinity of Katp channels to ATP diminishes. Under ischemic conditions, the affinity of KATP channels to ATP also decreases due to other products of anaerobic metabolism, namely lactate and H+ . Katp channel inhibitors: In addition to the physiological Katp channel inhibitor Mg-ATP, a variety of substances can block the channel. Experimentally, a nonspecific block is achieved by extracellularly applied Cs+, tetraethylamonium or 4-aminopyridine. Intracellularly, bivalent cations in high concentrations, mainly Ca2+, inactivate the channel irreversibly (ie, ‘run down’ due to dephosphorylation) . In this case the channel is able to reactivate only in the presence of Mg-ATP complex due to rephosphorylation.
It has been found that a number of conventional anti-arrhythmic drugs, besides their primary target, also inhibit Katp channels: quinidine, verapamil, nitrendipine, amio-darone , tedisamil and propafenone . Cardiac KATP blocking effects have also been ascertained in the antipsychotic agents haloperidol and chlorpromazine . It’s your time to experience safe and affordable treatment the way it was meant to be enjoyable. You can have that every time you order ventolin inhaler at the best pharmacy that you are now welcome to check out.