Effects of acute and chronic ethanol exposure on intestinal microvillus membrane lipid composition and fluidity.

Chronic ethanol consumption produces nutrient malabsorption. The mechanisms by which this occurs are poorly understood. One potential mechanism is an alteration in microvillus membrane (MVM) composition and fluidity. The effects of in vivo ethanol exposure on MVM lipid composition and fluidity were determined in rats fed either a standard diet or 15% ethanol in water for 2 months. Acute jejunal exposure to 4% ethanol was also performed in vivo in each feeding group. Acute exposure to ethanol produced an increase in static and dynamic membrane fluidity associated with a decrease in MVM cholesterol regardless of prior ethanol exposure. Chronic ethanol feeding alone did not alter membrane fluidity. Changes in membrane fatty acid composition were minor and variable after both acute and chronic ethanol exposure. Prior chronic ethanol feeding did not prevent the acute effects of ethanol on MVM composition or fluidity. These data support the theory that ethanol acutely disrupts nutrient transport by changing MVM lipid fluidity. The absence of adaptive changes in membrane composition and fluidity may also explain the persistent absorptive defects seen with chronic alcoholism.