Abstract
The effects of low (pCa 7.5 to 3) concentrations of intracellular
calcium ion on a single potassium channel in the sarcoplasmic reticulum
of canine heart ventricular muscle were investigated using a planar
lipid bilayer technique. The low concentrations were obtained by
mixing EGTA and calcium chloride. By varying the pCa of the cytoplasmic
face between 3 to 7.5, two novel effects were observed. First, an
increase in the intracellular Ca$^2+$ concentration produced
an increase in the unit current amplitude of open states; the voltage-current
relationship was ohmic at these concentrations. Second, an increase
in the Ca$^2+$ concentration increased the open probability.
Both these effects of Ca$^2+$ were dose-dependent, and were consistently
observed in all channels tested. Thus, the SR potassium channel observed
appears to belong to the class of Ca$^2+$-activated potassium
channels.
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- electrophysiology,
- enzyme
- expression,
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