Effects of fatty acids on BK channels in GH(3) cells.
Ca(2+)-activated K(+) (BK) channels in GH(3) cells are activated by arachidonic acid (AA). Because cytosolic phospholipase A(2) can produce other unsaturated free fatty acids (FFA), we examined the effects of FFA on BK channels in excised patches. Control recordings were made at several holding potentials. The desired FFA was added to the bath solution, and the voltage paradigm was repeated. AA increased the activity of BK channels by 3.6 +/- 1.6-fold. The cis FFA, palmitoleic, oleic, linoleic, linolenic, eicosapentaenoic, and the triple bond analog of AA, eicosatetraynoic acid, all increased BK channel activity, whereas stearic (saturated) or the trans isomers elaidic, linolelaidic, and linolenelaidic had no effect. The cis unsaturated FFA shifted the open probability vs. voltage relationships to the left without a change in slope, suggesting no change in the sensitivity of the voltage sensor. Measurements of membrane fluidity showed no correlation between the change of membrane fluidity and the change in BK channel activation. In addition, AA effects on BK channels were unaffected in the presence of N-acetylcysteine. Arachidonyl-CoA, a membrane impermeable analog of AA, activates channels when applied to the cytosolic surface of excised patches, suggesting an effect of FFAs from the cytosolic surface of BK channels. Our data imply a direct interaction between cis FFA and the BK channel protein.
Denson
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Department of Anesthesiolgy, Emory University School of Medicine, Atlanta, Georgia 30322, USA. ddenson@emory.org
Wang
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Worrell
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Eaton
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D000111:Acetylcysteine / Q000494:pharmacology; D000214:Acyl Coenzyme A / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism* / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000378:metabolism / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008560:Membrane Fluidity / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013329:Structure-Activity Relationship
D000214:Acyl Coenzyme A; D005227:Fatty Acids; D005231:Fatty Acids, Unsaturated; D016166:Free Radical Scavengers; D051036:Large-Conductance Calcium-Activated Potassium Channels; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated; D017382:Reactive Oxygen Species; C026563:arachidonyl-coenzyme A; D016718:Arachidonic Acid; D000111:Acetylcysteine