Nanomolar concentrations of ouabain block ethanol-inducible Na+,K(+)-ATPase activity in brain.
The effect of low concentrations of ethanol on Na+,K(+)-ATPase activity, defined as ouabain-inhibitable 86Rb+ (K+) uptake, was investigated in a crude synaptosome preparation which was subject to minimal subcellular fractionation procedures. Moderate (20-30%) but potent (EC50 = 3.8 mM) stimulation of total ouabain (1 mM)-inhibitable K+ uptake by ethanol was observed following incubation periods of up to 20 min. The activity of the ethanol-induced component of K+ uptake was antagonized by nanomolar concentrations of ouabain. Thus, the moderate stimulation of total ouabain-inhibitable K+ uptake by ethanol was attributable to the activation of a component of K+ uptake which was very sensitive (VS; IC50 = 2.8 x 10(-10) M) to inhibition by ouabain. Slightly higher concentrations of ouabain (10(-9) - 10(-6.6) M) stimulated K+ uptake above control (no ethanol or ouabain) in both the absence and presence of ethanol. The selectivity of the VS-ethanol interaction was demonstrated by the lack of any ethanol effect on two other components of ouabain-inhibitable K+ uptake which accounted for inhibition of K+ uptake by concentrations of ouabain above 10(-6.6) M and were defined as sensitive (S; IC50 = 10(-6) M) and insensitive (I; IC50 = 10(-4) M) to ouabain. These results define the ethanol-inducible component of ouabain-inhibitable Na+,K(+)-ATPase activity and promote the view that changes in Na+,K(+)-ATPase-dependent ion translocation may contribute to ethanol intoxication in vivo.
Foley
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TD
LCS, DICBR, National Institute on Alcohol Abuse and Alcoholism, NIH, Rockville, MD 20852, USA.
Linnoila
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M
D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D004790:Enzyme Induction / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012414:Rubidium Radioisotopes; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology
D012414:Rubidium Radioisotopes; D000431:Ethanol; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium