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Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
We investigated the effects of
clinically relevant ethanol concentrations (5-20 mM) on the
single-channel kinetics of bovine aortic smooth muscle maxi-K channels
reconstituted in lipid bilayers (1:1
palmitoyl-oleoyl-phosphatidylethanolamine:
palmitoyl-oleoyl-phosphatidylcholine). Ethanol at 10 and 20 mM
decreased the channel open probability (Po) by
75 ± 20.3% mainly by increasing the mean closed time (+82 to
+960%, n = 7). In some instances, ethanol also
decreased the mean open time (
40.8 ± 22.5%). The
Po-voltage relation in the presence of 20 mM
ethanol exhibited a rightward shift in the midpoint of voltage
activation (
V1/2
17 mV), a slightly
steeper relationship (change in slope factor,
k,
2.5 mV), and a decreased maximum Po (from
~0.82 to ~0.47). Interestingly, channels inhibited by ethanol at
low Ca2+ concentrations (2.5 µM) were very
resistant to ethanol in the presence of increased Ca2+ (
20 µM). Alcohol consumption in clinically relevant amounts may alter
the contribution of maxi-K channels to the regulation of arterial tone.
calcium dependent; voltage-gated potassium channels; planar lipid bilayer; arterial tone; alcohol
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