Effect of acetaldehyde on ethanol absorption in the canine jejunum.

The effects of acetaldehyde on ethanol absorption from the intestinal tract were studied using canine jejunal segment. A thirty-centimeter jejunal segment with intact vascular supply was isolated, and jejunal absorption studies were performed by administering a 17% ethanol solution (0.4 g/kg) into the lumen of the jejunal segment. In the control group, blood ethanol concentrations in the portal vein increased rapidly, with a peak level of 9.8 +/- 1.9 mM 30 min after administration. In the cyanamide-pretreated group, dogs were injected intravenously with cyanamide (100 mg/kg), an inhibitor of acetaldehyde dehydrogenase, 150 min before ethanol dosing. The blood ethanol concentration in the portal vein of this group, accompanied by a high acetaldehyde concentration, increased gradually, reaching a peak of 10.7 +/- 1.84 mM 120 min after ethanol administration. Each concentration gradient corresponded to the systemic circulatory order from the portal vein for ethanol concentration, and from the hepatic vein for acetaldehyde concentration. The absorbed amount of ethanol in the control and cyanamide-pretreated groups was 94.9 +/- 4.1% and 69.3 +/- 4.8%, respectively. Pharmacokinetic analysis indicated that a presence of high acetaldehyde concentration in the blood resulted in less ethanol reaching the systemic circulation (control: 7.34 +/- 2.95 h-1, cyanamide-pretreated: 1.08 +/- 0.75 h-1). The results also suggest that the absorption of ethanol from the intestine decreases when there is a high acetaldehyde concentration in the blood.