ATP-sensitive potassium channels and cardiac protection (part 8)
Katp channel openers: A group of prospective antihypertensive drugs that began to appear in the early 1980s fell into disrepute because of their hyperglycemic or other side effects. Later pharmacological studies, however, revealed the vasodilator effect on the coronary system at much lower concentrations than those used in the treatment of hypertension.Some of these drugs (such as nicorandil) were introduced into clinical practice. Moreover, certain protective effects of Katp channel openers on ischemic myocardium have been shown (see below). Soon afterwards it was found that they markedly abbreviate the action potential in cardiac preparations and that they act as Katp activators or openers . The vasodilating effect of these drugs (eg, pinacidil, nicorandil, cromakalim) is interpreted as a consequence of increased K+ conductance, hyperpolarization, restrained Ca2+ influx and, eventually, relaxation of the smooth vascular muscle . The exact molecular mechanism of their action has not yet been explained. Some kind of reduction of the Katp channel affinity to ATP may be anticipated because the action of the openers is readily blocked by KATP inhibitors including ATP in higher concentration . It is notable that cardiac mitochondrial Katp channels are 2000-fold more sensitive than the channels from cardiac sarcolemma to the opener diazox-ide . This should be taken into account in studying the pharmacological effects of Katp channel openers. You will always be glad to know there is a perfect pharmacy waiting for you whenever you need flovent for asthma and would like to make sure you are taken best care of as a customer and patient.