Role of intestinal bacterial overgrowth in ethanol production and metabolism in rats.

To investigate the role of intestinal bacterial overgrowth on the production and metabolism of ethanol, rats with a jejunal self-filling diverticulum (blind-loop) were compared to controls with a self-emptying diverticulum. Both endogenous ethanol and acetaldehyde were found in the blind-loop contents. Intragastric administration of sucrose produced a marked increase in acetaldehyde and acetate in the portal venous blood, with only a modest elevation of ethanol. Blind-loop contents readily oxidized ethanol to acetaldehyde in a concentration-dependent manner and more actively under aerobic than anaerobic conditions. This oxidation was inhibited by antibiotics and was reproduced with isolated microorganisms. Intragastric administration of ethanol to rats with blind-loops markedly increased acetaldehyde and acetate concentrations in the portal vein and, to a lesser extent, in the systemic blood, compared with the controls. By contrast, both portal and systemic blood ethanol concentrations were lower in the rats with a blind-loop compared with controls, even though the amounts of ethanol retained in the digestive tract were similar. A dose of ethanol about twice as large as in controls was required to produce similar systemic blood levels. Both in rats with a blind-loop and in the controls, the areas under the curve of blood ethanol concentrations were smaller after intragastric than after intravenous ethanol administration (1 g ethanol/kg body wt). This difference was exaggerated in the rats with a blind-loop. Thus, a considerable amount of ethanol is oxidized in the gastrointestinal lumen of rats with a blind-loop. The resulting high concentrations of acetaldehyde, both in the intestinal lumen and the portal blood, may have deleterious effects on the gastrointestinal mucosa and the liver.