ischaemic preconditioning of the human heart. - Leicester Research ...

and relationship of this channel to myocardial protection will be discussed in detail
below
[on channels are proteins that span cell membranes and make them permeable to
physiological ions, with channel proteins being selective to particular ions. An aqueous
pore runs through the protein from inside to the outside of the membrane, through which
ions can flow passively, down the electrochemical gradient. This mode of passive flow
through the K+ channel is in common with that of other types of ion channel. Electrical
current is carried when there is a flow of ions through the channel, and high rate of ion
allows currents to be measured even from a single channel, as well as from whole cells
by the electrophysiological technique of patch clamping.
The pore of most K+ channels can be opened or closed, that is to say they are gated,
by a conformational change in the protein molecule. Potassium channels are specific for
K+, but differ by the factors which regulate gate opening or closing, or in the rate of K+
flow through an open channel. Channels can be further subdivided depending on whether
gating is dependent primarily on membrane potential, voltage gated channels, or whether
it is linked to binding of a specific chemical ligand, ligand-gated channelsI- although
ligand-gated channels ofien show some voltage sensitivity as well. ATP-sensitive K+
channels have a specific K+ selective pore, and intracellular ATP plays an important role
in their gating. These channels provide a unique link between potassium permeability and
action potential to cellular metabolism. K., %., -p channels are found in excitable tissues such
as the heart, skeletal and smooth muscle, neurones and pancreatic P-cells, and link the
excitability of the cells to the metabolic state [9].
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