Effects of Aliphatic Alcohols and Aldehydes on Fluidity of Spin-Labeled Synaptosomal Plasma Membranes
Synaptosomal plasma membranes from Swiss-Webster mice were spin-labeled with 5-doxylstearic acid. By electron paramagnetic resonance techniques an order parameter was measured. A decrease in the order parameter reflected an increase in membrane fluidity. In confirmation of our previous work, ethanol decreased membrane order. Pentanol also showed a concentration-related decrease in the order parameter in the range of 23 to 87 mM. At equimolar concentrations, pentanol was about 9 times more effective than ethanol. Acetaldehyde had no effect on membrane fluidity at concentrations that might be found in vivo during ethanol oxidation (23 or 227 μM) but a very high concentration, 2.3 mM, produced a small decrease in the order parameter comparable to the effect of an intoxicating concentration of ethanol. Valeraldehyde also had a slight fluidizing effect and appeared very roughly three times more potent than acetaldehyde. This study shows that the fluidizing effects of ethanol are not shared by its aldehyde metabolite at relevant concentrations. The fluidizing effects of aldehydes are slight but they increase with concentration and with chain length.
We previously showed by a sensitive electron paramagnetic resonance (EPR) technique that low concentrations of ethanol increased the fluidity of mouse erythrocyte and synaptosomal plasma membranes (Chin and Goldstein, 1977a,b) and that tolerance developed to this effect (Chin and Goldstein, 1977c). However, some of the acute and chronic effects of ethanol have been attributed to its primary metabolite, acetaldehyde, which is thought to act either alone or after combining with biogenic amines to form tetrahydroisoquinolines (Cohen, 1976). In the present study we have compared the membrane action of acetaldehyde to those of ethanol, using concentrations that circulate in vivo during ethanol oxidation. Pentanol and valeraldehyde were also tested, to assess the influence of chain length.
KeywordsElectron Paramagnetic Resonance Biogenic Amine Membrane Fluidity Aliphatic Alcohol Ethanol Oxidation
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