Detergents, dimeric G beta gamma, and eicosanoid pathways to muscarinic atrial K+ channels.
Control experiments for the direct effects of G protein beta gamma-subunits (G beta gamma) on muscarinic atrial K+ channel [K+ (ACh)] currents have produced different results (Nature Lond. 327: 21-22, 1987; Nature Lond. 325: 296-297, 1987; Cold Spring Harbor Symp. Quant. Biol. 53: 365-373, 1989). A recent view is that stimulation is indirect via phospholipase by (PLA2) and arachidonic acid (AA) metabolites (Nature Lond. 337: 504-505, 1989). On reexamination we found that 1) the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) used to suspend beta gamma stimulates atrial K+ (ACh) currents by itself, and the effects are concentration and Mg2+ dependent; 2) CHAPS stimulates atrial ATP-sensitive K+ channel and inwardly rectifying K+ channel currents; 3) blockers of eicosanoid pathways have nonspecific effects on atrial K+, Ca2+, and Na+ channels. We have confirmed that detergent-free, hydrophilic G beta gamma-subunits inhibit K+ (ACh) currents. Stimulatory effects of dimeric G beta gamma could not be separated from stimulatory effects of detergent, and blockers of PLA2 or lipoxygenase pathways do not clearly establish the significance of these pathways to atrial K+ (ACh) currents.
Yatani
A
A
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.
Okabe
K
K
Birnbaumer
L
L
Brown
A M
AM
D000818:Animals; D002793:Cholic Acids / Q000494:pharmacology*; D003902:Detergents / Q000494:pharmacology*; D015777:Eicosanoids / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000494:pharmacology*; D006325:Heart Atria; D009116:Muscarine / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D013501:Surface-Active Agents / Q000494:pharmacology*
D002793:Cholic Acids; D003902:Detergents; D015777:Eicosanoids; D015221:Potassium Channels; D013501:Surface-Active Agents; D009116:Muscarine; D019204:GTP-Binding Proteins; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate