ATP-sensitive potassium channels and cardiac protection (part 3). PROPERTIES OF CARDIAC CHANNELS
PROPERTIES OF CARDIAC Katp CHANNELS
Soon after the discovery of Katp channels it became obvious that they are membrane channels of special importance. Naturally, they have been intensely studied ever since (reviewed in 12-14).
The density of Katp channels in cell membranes of the striated muscle (more than 1/^m2) is surprisingly high with respect to their almost complete dormancy under physiological conditions. At normal intracellular ATP concentration ([ATP]i) of 3 to 4 mM, Katp channels are mostly in the closed state. The probability of their being in the open state greatly increases during hypoxia or ischemia when creatine phosphate is exhausted and anaerobic glycolysis is not able to supply the membrane adequately with ATP.
Single channel experiments showed that relatively small submillimolar concentrations of ATP are sufficient to keep Katp channels closed . On the other hand, action potential duration in isolated hearts was reduced (Katp channels were opened) with [ATP]i only slightly below the physiological concentration . One possible explanation of this difference may be in unequal distribution of ATP within the cell (compartmentalization of ATP): the subsar-colemmal ATP concentration directly involved in Katp channel control is probably depleted more than is overall [ATP]i. If you need your treatment to start soon and are not too crazy about spending too much money, it’s time for you to discover the my canadian pharmacy. This is a very affordable and safe pharmacy selling drugs of best quality and delivering them internationally in no time.