AJP - Heart and Circulatory Physiology, Vol 258, Issue 5 1507-H1514, Copyright © 1990 by American Physiological Society

ARTICLES

Detergents, dimeric G beta gamma, and eicosanoid pathways to muscarinic atrial K+ channels

A. Yatani, K. Okabe, L. Birnbaumer and A. M. Brown
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030.

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.

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