Effect of Ethanol on the Palmitate-Induced Uncoupling of Oxidative Phosphorylation in Liver Mitochondria

V. N. Samartsev^*, K. N. Belosludtsev, S. A. Chezganova, and I. P. Zeldi

Mari State University, pl. Lenina 1, Yoshkar-Ola, 421001 Russia; fax: (836-2) 45-4581

^* To whom correspondence should be addressed.

Received October 4, 2001

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The effect of ethanol on the uncoupling activity of palmitate and recoupling activities of carboxyatractylate and glutamate was studied in liver mitochondria at various Mg²⁺ concentrations and medium pH values (7.0, 7.4, and 7.8). Ethanol taken at concentration of 0.25 M had no effect on the uncoupling activity of palmitic acid in the presence of 2 mM MgCl₂ and decreased the recoupling effects of carboxyatractylate and glutamate added to mitochondria either just before or after the fatty acid. However, ethanol did not modify the overall recoupling effect of carboxyatractylate and glutamate taken in combination. The effect of ethanol decreased as medium pH was decreased to 7.0. Elevated concentration of Mg²⁺ (up to 8 mM) inhibits the uncoupling effect of palmitate. Ethanol eliminates substantially the recoupling effect of Mg²⁺ under these conditions, but does not influence the recoupling effects of carboxyatractylate and glutamate. It is inferred that ADP/ATP and aspartate/glutamate antiporters are involved in uncoupling function as single uncoupling complex with the common fatty acid pool. Fatty acid molecules gain the ability to migrate under the action of ethanol: from ADP/ATP antiporter to aspartate/glutamate antiporter on addition of carboxyatractylate and in opposite direction on addition of glutamate. Possible mechanisms of fatty acid translocation from one transporter to another are discussed.

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KEY WORDS: uncoupling, fatty acids, ethanol, glutamate, carboxyatractylate, aspartate/glutamate antiporter, ADP/ATP antiporter, uncoupling complex, liver mitochondria

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